superkret, 11 months ago

You could do the following to improve things somewhat:

type about:config into the address bar
read and accept the warning
type browser.tabs.tabMinWidth into the search field
set value to 0

It will let you open a lot more tabs before scrolling away, but stll not an infinite amount.
Now what’s keeping you from getting arbitrarily narrow tabs are the icons displayed on them.
Removing them is more difficult:

Type about:config into your address bar. Promise you’ll be careful and proceed. Now type toolkit.legacy into the search bar on the about:config page and hit enter. Look for an option named toolkit.legacyUserProfileCustomizations.stylesheets and click the toggle on the far right side to set this option to true.

Type about:support into your address bar. Follow along the left side of your screen until you see a row titled Profile Folder. Directly to the right of this you should see an Open Folder button. Click on this.

A window should launch in Windows File Explorer that will navigate to your Firefox profile’s folder. Go ahead and create a new folder inside this profile folder. You can do this by either clicking the new folder icon in the top left or by using the keyboard shortcut, CTRL + Shift + N. Rename this new folder as “chrome” (do not include the quotation marks and ensure all letters are lowercase). Open this new chrome folder.

Right click in the empty space inside the folder, click on new, and click on Text Document. Now open this new text file. Copy and paste the following into it:

<span style="color:#323232;">.bookmark-item > .toolbarbutton-icon {
</span><span style="color:#323232;">    display: none !important;
</span><span style="color:#323232;">}
</span><span style="color:#323232;">
</span><span style="color:#323232;">#PlacesToolbarItems > .bookmark-item > .toolbarbutton-icon[label]: {
</span><span style="color:#323232;">    margin-inline-end: 0px !important;
</span><span style="color:#323232;">}
</span><span style="color:#323232;">
</span><span style="color:#323232;">.tabbrowser-tab .tab-icon-image {
</span><span style="color:#323232;">display: none !important;
</span><span style="color:#323232;">}  
</span>

Click on ‘File’ in the top left and then ‘Save As…’. Towards the bottom of the file save window, change the name of the file to “userChrome.css” (once again, do not include the quotation marks and ensure everything is lowercase except the ‘C’ in ‘Chrome’).

Underneath the File Name box, you’ll see a Save as Type box that should currently be set to Text Documents (*.txt). Change this to All Files. Click on Save. Now go back into Firefox and type about:profiles into your address bar. Click on the Restart Normally… button in the top right corner of the page.