Try this for the Folder Pane:

#folderTree > treechildren {
  font-size: 12pt !important;
  font-family: Verdana !important;
  background-color: lightgrey !important;
  color: navy !important;
}
#folderTree treechildren::-moz-tree-row {
height: 18px !important;
min-height: 18px !important;
}

Thanks, it works.

I've done a bit of tweaking/experimenting and may soon reach the level of novice Thunderbird .css writing.

Do you have a link or something that lists the typical entries that are currently used by thunderbird in the userChrome.css file?

It's obviously specific to Thunderbird.

I could be wrong but I think one of my problems was that leaving in the namespace line prevented both the #folderTree and the #threadTree being used. I have desired line spacing now in both lists. When I added your above code, my message list #threadTree settings were ignored but the #folderTree worked. Both worked after removing the namespace.

The adjustments I am still working on are just font, font size and background color.

Thanks again

I don't know of a central source of TB css references, but there are plenty of examples revealed through basic web searches.

The namespace declaration is no longer needed, but it shouldn't do any harm if it's included.

Thank you, sfhowes. Now where does this marking go. Is it an addition or alteration to a CSS file and, if so, which CSS file is it? I am presuming the code is XML?

Oh, and this is for the folder list - what about the message list. It is important to me in that I have been using Thunderbird since shortly after initial launch and I have several thousand messages distributed across several dozen folders.

Just follow these directions: Help/Troubleshooting, Profile Folder, Open Folder, close TB, create a new folder named chrome, create a new document in chrome with a text editor, name it userChrome.css, Save as type: All files *.*, copy in the above code, change the numbers as desired. Double-click toolkit.legacyUserProfileCustomizations.stylesheets to true in Options/General/Config. editor, restart TB.

For the message list, same code except replace folderTree with threadTree.

sfhowes, thank you for the prompt reply. I will give that a try.

Ok. And the next problem in there; the subject disappears when I roll the cursor over it.

Ok. And the next problem in there; the subject disappears when I roll the cursor over it.

This a known W7 bug: https://support.mozilla.org/en-US/questions/1312243

Should be resolved in 78.5 next week.

The solution suggested won't work as the file userChrome.css doesn't exist on my main use PC or any other PCs with Thunderbird installed. Probably because my browser is Firefox and have never installed Google Chrome on any others I own.

Is there a template of the userChrome.ass file that can be merged into my system and modified using the about:config utility?

The OS is an OEM Windows 7 Pro, 8 Gb Ram, 2Tb HDD an a Dell.

My perception is Mozilla Foundation have caught the "big corporations disease" and rolled out the "new and improved" version of Thunderbird without any market research.

Jesus, there has to be an easier way to change message line spacing than having to hack .css files.

Why would the paragraph formatting controls be removed from v78? Makes me want to stop using the program.

@billb1 - Flexibility is the key to satisfaction. Unfortunately, nothing seems to have been done to retain the format in earlier versions. On the other hand, using the "chosen solution" above allowed me to make it better than the previous version. A plus for me is that in the past I had no need to use Content Style Sheets (CSS), so this was a welcome exercise.

Using Thunderbird 78 has become a real nightmare. After using TB for the past few eons, I find that I cannot get the line spacing or font size that I want. ALL the solutions offered here are useless to me, since they are global (changing the pixels in the config editor, using a global font in the userChrome.css, which screws up calendar font size, etc.)

In my userChrome.css I have the following lines:

#threadTree > treechildren::-moz-tree-cell-text(unread) 

{ font-size: 19pt ! important; font-family : Comic Sans MS !important; color: #CC0000 !important; }

treechildren:-moz-tree-cell-text(read) { font-size: 22pt ! important; font-family : Arial !important;

The first group (for unread messages) works, and I can determine the color, size, etc. for those lines of my inbox. The second group (for read messages) is frozen at some font family and size NOT of my choosing, and ignores all my attempts to make it readable, let alone nice looking. WHAT AM I DOING WRONG? The .css file is in the right folder (which is why some of it works), but parts of it (not only the INBOX) are refractory to all my attempts. Help, please!