Modifying TB 78 to use TB 68 Folder Pane Icons
I've tried TB 78.0, but have now gone into my backups and restored TB 68.10 for the simple reason that I HATE the new vector outline monochromatic icons in the folder pane. (And, yes, I know they can each have their colour changed, but each icon remains monochromatic - just the simple vector outline in the one colour).
If anyone already knows or can work out how to amend TB 78 to use the TB 68 folder pane icons (or any other equally agreeable set) could you please let me know how. Otherwise I will just stay on 68.10 indefinitely. (After all, with 6 plugins and some userChrome.css and about:config tweaks, 68.10 does everything I want with my 6 assorted provider IMAP mail accounts, including syncing the Outlook and Gmail calendars, and has been rock solid, so i have no positive reason to change, and certainly not to put up with what is to me a dull and ugly interface with the move to the monochromatic vector icons.)
I'm sure it is possible to substitute the old icons in the folder pane, as in Firefox I found and used a set of instructions for userChrome.css and the icon pngs to replace the similar, equally dull and monochromatic vector bookmark folder icons in post-57 Firefox with the old FF-56 yellow folder pngs. So I'm sure the same can be done here for the folder pane icons. Unfortunately I only know enough to follow such instructions, not to come up with the method myself.
Thank you to anyone who can help. But please do NOT reply with instructions on how to change the colour of the vector icons - I know, have tried it, the results are not good enough. Or telling me I should just like the vector icons - I do not and will not. The only reply that will answer this question is one with the userChrome.css to override the folder pane vector icons with a set of the old icon pngs.
Alla svar (2)
There is no option to change the icons that is available to the non developer types. (including me there) Not that usechrome itself requires preference edits to work now apparently.
Note that the OLD PNG files are not suitable for the modified setup, or that is what I have been lead to believe. Something about scaling.
I presume that the toolkit.legacyUserProfileCustomizations.stylesheets flag still exists in 78 (I didn't check before reverting to 68).
The point about scaling is that they are using the vector icons, which will scale, as opposed to the old png files, which don't (or not well,as they are very small so enlarging them may not look good). But that doesn't matter as I only want them at the current size anyway.
The situation is exactly analogous to the bookmark folder icons in Firefox from FF 57 on, where they also moved to monochrome vector graphics. But it IS possible to revert. In my Firefox I have my own userChrome.css changing colours in parts of the interface, menu backgrounds and whatnot. But I also installed from https://www.userchrome.org/what-is-userchrome-css.html#colorbookmarkfolder the 'old icons version' wherewithal to replace the vector bookmark folder icons with the old FF 56 bookmark png icons, which still works in FF78. There's a .css file, which I call at the beginning of my userChrome.css, and all the old png folder icons also in the chrome folder. And it works perfectly.
I see no reason why there can't be a similar .css file for Thunderbird 78+ that can be called at the beginning of the userChrome.css (which I already have changing some panel colours, font sizes etc) and replaces the folder pane vector icons with the old pngs (which need extracting so they can also be put into the chrome folder). This is fundamentally the same as replacing the bookmark folder vector graphics with the old pngs in Firefox. My only problem is that I don't know how to write the css. So I'm asking if anyone else can (or has). A posting that gives a link to a css file that does that is the only actual post that will 'solve this problem'.
It's possible. It just needs someone with the css skills to do it. For someone with the skills, looking at the css file that restores the old bookmark icons to FF 57+ should give a good idea how to restore the old folder pane icons in TB. Sadly I don't have the css skills base to understand it myself.