This seems to work:—

/* Source file https://github.com/MrOtherGuy/firefox-csshacks/tree/master/chrome/multi-row_bookmarks.css made available under Mozilla Public License v. 2.0
See the above repository for updates as well as full license text. */

/* Makes bookmarks toolbar span multiple rows */

#PersonalToolbar{
  --multirow-bmb-n-rows: 3; /* Control how many rows are shown before scrolling */
  --multirow-bmb-row-margin: 2px; /* Control how much spacing is between rows */
  max-height: none !important;
}
:root[BookmarksToolbarOverlapsBrowser] :where(#PersonalToolbar){
  height: unset !important;
}

#PlacesToolbar > hbox:not(#PlacesToolbarDropIndicatorHolder){ 
  display: block;
  width: 100vw;
}

#PlacesToolbarItems{
  display: flex;
  flex-wrap: wrap;
  /* --uc-bm-padding is defined in autohide_bookmarks_toolbar.css */
  max-height: calc(var(--multirow-bmb-n-rows) * (4px + 1em + (2 * (var(--multirow-bmb-row-margin) + var(--uc-bm-padding,var(--bookmark-block-padding)))))) !important;
  overflow-y:auto;
  scrollbar-color: var(--lwt-accent-color) var(--toolbar-bgcolor);
  scrollbar-gutter: stable;
  scrollbar-width: thin;
}

/* Hide the all-bookmarks button */
#PlacesChevron{ display: none }

/* Add some spacing between rows */
#PlacesToolbarItems > .bookmark-item{
  margin: var(--multirow-bmb-row-margin) 3px !important;
  visibility: visible !important; /* Just in case they would be hidden for some reason */
}

Hey I tried that and it did not produce any result, lets keep trying, thanks.

Do you this CSS code?

• https://github.com/MrOtherGuy/firefox-csshacks/tree/master/chrome/multi-row_bookmarks.css

It is not that difficult to create userChrome.css if you have never used it.

The first step is to open the "Help -> Troubleshooting Information" page and find the button to access the profile folder with the random name (xxxxxxxx.default-release).

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

You can find the button to go to the profile folder under the "Application Basics" section as "Profile Folder -> Open Folder". If you click this button then you open the profile folder in the Windows File Explorer. You need to create a folder with the name chrome in the profile folder with the random name (name is all lowercase). In the chrome folder you need to create a plain text file with the name userChrome.css (name is case sensitive). In this userChrome.css text file you paste the text posted. On Mac you can use the TextEdit utility to create the userChrome.css file as a plain text file.

In Windows saving the file is usually the only time things get more complicated because Windows can silently add a .txt or .css file extension and you end up with a file like userChrome.css.txt or userChrome.css.css. To avoid this, you need to make sure to select "All files" in the "Save File" dialog in the text editor.

You need to close (Quit/Exit) and restart Firefox when you create or modify the userChrome.css file.

More info about userChrome.css/userContent.css in case you are not familiar:

• https://www.userchrome.org/what-is-userchrome-css.html
• https://www.userchrome.org/how-create-userchrome-css.html
• https://www.userchrome.org/firefox-changes-userchrome-css.html

You need to set this pref to true in about:config to enable userChrome.css and userContent.css in Firefox 69+.

• about:config => toolkit.legacyUserProfileCustomizations.stylesheets => true
• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Right, I followed the instructions there which are similar to the previous ones for the outdated code, it produced a broken result, the other one I tried failed to produce an effect, and the one here I just tried which was provided did not produce anything either, but I have done as much regarding the css file, but my bookmarks bar is not affected.

Any luck with the code posted here?

• /questions/1447710 userchrome.css

That's very odd as I've just tried it again, on a different computer to the one I used earlier, and it works fine. I've also confirmed that I'm on Firefox 129.0.1.

The only thing I can suggest is that you check that toolkit.legacyUserProfileCustomizations.stylesheets really is set to true and the chrome sub-directory and userChrome.css file are spelt properly. As Cor-er says, some text editors can put .txt on the end even if you don't want it creating a file called userChrome.css.txt which won't work. If you are using Windows Explorer it can hide extensions so right-click userChrome.css and choose properties to see its full name to make sure.

That said a "Broken result" would seem to show that the files are at least been read. No result at all is much more mysterious.

Have you got any other things in your userChrome.css file?

I went around and tried to find the code that was functional but butchered the screen, all I could find are non-functional ones, so I have been saving as general file type from the userchrome css type file which retains that attribute in the saving I have been doing, it has not been working.

Did you try to use only this code in userChrome.css to prevent other code interfering?

toolkit.legacyUserProfileCustomizations.stylesheets - I expressly rechecked this and it was set to true, as it does not look by default, per what I read elsewhere. I have notepad set as the default program for this, even though we are not saving in text. If I should place the userchrome file in the other profile folder that has the JSON file in it as well would help, then suggest as much. For what its worth, I have a slew of folders which would fill up the bars and overflow section.

Can you attach a screenshot that shows what issues you have?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

When I tested the other code I ditched the rest of it and replaced it later after the test, I copied the .css to desktop and proceeded to edit it in the chrome folder.

For what it's worth there are a slew of folders, not websites which would fill up the space, and reach the adjusted overflow menu.

SOLVED - At some point in the editing and so forth, the file got appended with .css in the filename, it was never a text file but it was .css at the end of it, while being that type as well. So lol, that Ghostbuster referencing one was the one that was broken, and further ones did not matter because of that in fact, so alright then.

Good stuff All.