The icons next to the names of your bookmarks are called favicons. I don't think it's possible to remove them without the use of custom CSS code.

Thanks – I came across the term 'favicon' after I posted my query. Some years ago I managed to get rid of them by means of a userChrome.css file, but after a recent Firefox Refresh they returned and neither my old CSS file nor any of the strings of code I've found online will shift them. (One batch of code I found did replace them with a generic 'globe' graphic, which was a slight improvement, but its favicon returned after I'd used a particular bookmark.) As others have commented before me, it's surprising that the choice of favicon or text or both for bookmarks isn't available in the standard FIrefox customisation menus. Anyway, a CSS file that works would be greatly appreciated.

OK, I've now managed to solve the problem myself, as follows:

1. In a text editor / word-processor, create a file containing this:

1. personal-bookmarks .bookmark-item:not([container]) .toolbarbutton-icon { display: none !important; }

2. Save the file as a text file (not RTF) called userChrome.txt.

3. Change the name of the file to userChrome.css.

4. Create a folder called chrome, and move the userChrome.css file into it.

5. In Firefox, go to Help > More Troubleshooting Information > Application Basics > Profile Folder, and click Show in Finder alongside this to open the Profile Folder itself.

6. Drag the newly created chrome folder into the Profile Folder.

7. In Firefox, type about:config in the address space and press Return.

8. Accept the warning of risk, then on the next page click on Show All.

9. Scroll down to toolkit.legacyUserProfileCustomizations.stylesheets and click in the last-but-one column to change the second column to read 'true'.

10. Quit Firefox and restart, and the favicons in the visible part of the bookmarks toolbar should now have disappeared.