Hi jk04120, as you are experiencing right now, Firefox uses a single-line tab bar with buttons at each end to scroll when there are more tabs than will fit in the available width.

If you had a multi-row tab bar before in Firefox 57 or later, most likely you had created a userChrome.css file. This should still be available in your old profile folder, which would be on your Desktop in the Old Firefox Data folder. Can you find that approximately here:

[Desktop]\Old Firefox Data\[profile.folder]\chrome\userChrome.css

You can re-use that userChrome.css file but please review all the setup steps to make sure it ends up in the right spot and enabled for Firefox 69:

https://www.userchrome.org/how-create-userchrome-css.html

Note that in Firefox 69 and later you need to set this pref to true on the about:config page to enable userChrome.css and userContent.css in the chrome folder. This pref is false by default in newly created profiles like when you use the refresh feature in Firefox.

• toolkit.legacyUserProfileCustomizations.stylesheets = true
• https://www.userchrome.org/firefox-changes-userchrome-css.html

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Thanks. I have copied the userChrome.css file (which I suspect was created by TabMixPlus prior to the web extensions switchover -- I don't recall doing so) and set the about:config entry as indicated above. I'm now sort of halfway there, but in worse shape than before.

I see one row of tabs (above the line with the URL bar and bookmark tab bar, not below them, but I can live with that). The button that shows all tabs has disappeared, but I can see commented-out entries in the userChrome.css file that read

#tabbrowser-tabs .scrollbutton-up, #tabbrowser-tabs .scrollbutton-down, 

so I assume I can use those to simulate that listing.

When tabs overflow from that first line, rather than creating a new line, I see a single tab for the page I'm looking at overlaid on the URL bar.

So my guess is that something in the userChrome.css file or elsewhere needs additional modification.

No, uncommenting those fields did not restore the scroll bars and I don't get a "+" New Tab button either, so I'm worse off than I was before.

The comment at the top of the userChrome.css file (which either TabMixPlus or I presumably copied in April 2018), reads /* MULTI-ROW TABS

  based on https://www.reddit.com/r/FirefoxCSS/comments/7dclp7/multirow_tabs_in_ff57/ 
  If tabs are too narrow, go into about:config and adjust browser.tabs.tabMinWidth

• /

if that is of any help.

For the list all tabs button you need this code:

/* LIST ALL TABS - always visible */
#tabbrowser-tabs ~ #alltabs-button { visibility: visible !importan; }

cor-el, Code inserted. No change. That button may, of course, appear on one the lines I can't see.

My guess is that all of the lines are there, they are just hidden by the URL bar, and maybe the bookmark bar, that are in front of them except for the active tab if it is in the second or third line. If that is correct, we need code to either move those bars/lines down or to put the tab bars below the bookmark bar, pushing the page frame down.