Recently I found this developer who has published dozens of small, useful extensions for firefox. Nothing groundbreaking that I know of but everything looks to have been made with care to efficiency and minimal permissions to do one thing well. Each has its own github repo where the developer responds to issues.
Many QOL improvements without having to install a large extension with additional functions you may not need.
I have nothing to do with this person but I was impressed so thought I would share.

dev:

extensions:

  1. Access URL Parts: quickly navigate to aka. access parts of the current url (breakcrumbs) , by either draggin them into the current tab context or opening them into a seperate tab
  2. Auto Close Tabs: auto closes idle tabs when not active, hidden, playing audio, highlighted/selected, pinned or contain visible text input field with text in them.
  3. Automate Click: This add-on can automate click actions that users might have to perform when visiting a website. For example accept or reject cookie consent messages.
  4. Auto Updating Bookmarks: auto updating bookmark on navigation in the same domain, for example to read webcomics and continue from where you left off
  5. Block Suspicious Downloads: Block the download of files which contain suspicious substrings like “.exe” but allows to quickly make exceptions
  6. Bookmark Branch Porter: Allows to import or export a branch of the bookmark tree as json or html
  7. Bookmark Router: Place bookmarks into specific folders based on url regex matches
  8. Bookmark Tabs: Saves selected or all tabs into a timestamped bookmark folder for later use
  9. Close All Duplicate Tabs: Shows the total amount of duplicate tabs and allows to quickly and easily close them - Leaving the oldest ones open.
  10. Close All Same Origin Tabs: Shows the total amount of same origin tabs and allows to quickly and easily close them - Leave only the oldest tabs open.
  11. Close Other Duplicate Tabs: Shows the amount of duplicate tabs the current tab has and allows to quickly and easily close them
  12. Close Other Same Origin Tabs: Shows the amount of tabs with the same origin as the currently active tab has and allows to close the others with one click
  13. Copy Image as DataURL: This add-on adds a right click menu to copy a image as a base64 data URL
  14. Copy Link Extras: Adds a link context menu quickly copy a link text, a link text with url and also allows copying the url with and without parameters.
  15. Copy Tabs: Copy tabs as hyperlinks or as plaintext URLs, similar to MS Edge, but actually even better since this addons supports copying mutliple tabs at the same time.
  16. Dont Open Duplicate Tabs: Addon, to prevent the opening of tabs with urls, which are already opened.
  17. Double Click Dictionary: Double-click any word to view its definition in a pop-up bubble Fork of the “Dictionary Anywhere” addon initally made to make it usable for android but now adds a couple of more features/improvements
  18. Export Bookmarks as Text: Export all bookmarks or a branch of the bookmark tree in a text only format
  19. Fix Missing Bookmark Titles: Fix Missing Bookmark Titles
  20. Get Tabs Infos: Get tab information in a user defined custom format string
  21. Handle With: Run external application from the Context (Right Click) Menu
  22. Image Control: Simple addon, to prevents the loading of images either via a black or whitelist based on domain (aka. origins ) It can help to safe traffic on mobile connections and might even make some sites more readable.
  23. Import Bookmarks from File: Quickly import all urls inside a textfile into a bookmark folder
  24. Indicate Bookmarked Links: Indicate on hover if a link has already been bookmarked
  25. Last Visit Search: A “history” addon which creates a searchable table gallery with thumbnail images of visited sites and some meta information
  26. Limit Active Tabs: Limits the number of active tabs by unloading older tabs
  27. List Feeds: Detects and lists feeds (rss, atom, json) of a page.
  28. Load Background Tabs on Select: Prevents tabs which are opend in the background from loading until they have been manually activated once
  29. Load Tabs Sequentially: Load multiple opened tabs sequentially
  30. LocalStorage Editor: Add, edit, copy, remove, export and import localand sessionstorage data
  31. Mute Unfocused Tabs: Allows to manage the mute state of a group (or all) tabs to only keep the currently focused one of the group unmuted and mute the others. Quick-Change via Toolbar Button and permanent ex/inclusion via preferences
  32. Notify on Events: tiny addon that can display a notification and optinally play a sound when a download starts, completes or fails, which is a little more noticeable than the default download icon change
  33. Open in Sidebar: Open links, pages, tabs or bookmarks into the sidebar.
  34. Open in Temp Container: Open a tab, page, link or bookmark in a new empty temporary container that removes itself, when the last tab it contains get removed
  35. Open Right Beside: Open new tabs right beside their opener (aka. parent) tab or beside the currently active tab
  36. Open Tabs from Clipboard URLs: Open tabs from the content of the clipboard, allows to open large number of tabs simultanisouly, by loading them in a discarded state, meaning that they will load the content only when they get selected
  37. Open Tabs from File: Reads URLs from a text file and opens them as unloaded tabs
  38. Open with Selection: Open Tabs with placeholder URLs and text selection
  39. Origin Lock: Lock a Tab to the currently active origin. (proto+domain+port) If a navigation in the main_frame is triggered that doesnt target the same origin, the navigation will be canceled an instead a new tab will be opened with the target url.
  40. Persistent Element Remover: This addon can remove elements (annoyances) which are inserted dynamically after pageload.
  41. Quick Image Print: adds a context menu entry which allows to directly open the print dialog on images
  42. Quick Save / Skip Save as: Direclty save elements without having to specify the name or save path. Skips the Save as Dialog
  43. Save Website as Image: Simple addon, to save the full website of one or more tab as a png image either via a click on the toolbar icon or via a custom shotcut
  44. Select Same Origin Tabs: Quickly select tabs with the same origin (protocol + domain + port) in the current windows to move, close or otherwise process.
  45. Select Tabs Advanced: Powerful tab selection addon with a bunch of one click options but also allow the user to create custom selection rules, based not only on tab attributes, but can also incorporate site parameters and content.
  46. Send to CyberChef: Adds a context entry to send selected text to a CyberChef instance for further analysis
  47. Show QRCode: Displays the active url (or any selected link or text) as a qrcode for easy sharing between devices with a qrcode scanner like mobile/smart phones and tablets. Also allows saving and copying to the clipboard for pasting in other programms
  48. Side Translate: Translate selected text in the sidebar with a translation history
  49. Startup Tabs: Open a set of bookmarks as tabs on browser startup by simply selecting a bookmark folder which contains them.
  50. Table to CSV: Save HTML Tables, CSS Pseudo/DIV Tables or Lists (UL/OL) as a comma seperated values (CSV) file which can be opened with any spreadsheet processor (e.g. excel, libreoffice-calc,gnumeric) for further processing and conversion (e.g. to xls or ods)
  51. Tabs Media Controller: Control Audio and Video Elements from all tabs from the toolbar button popup menu
  52. Tab Stack: Just another tab grouping addon. Since firefox has no native support to add something like a “stacked” tab group, this is the closes i could come up with.
  53. Toolbar Countdown: Shows a custom countdown in the toolbar. Well technically it only shows the most significant part. (days) at least until none are left then it gradually drops goes to hours, then minutes and finally seconds.
  54. Visits Counter: Indicates how often the open website has been visited before, by showing a visited counter on the toolbar icon
  55. Youtube Bookmark Cleanup: Remove Duplicate Youtube Video Bookmarks from a folder