Thunderbird: Installed themes show up only in the extensions tab
After receiving an email about an update in TB 68 regarding theme support, I dusted off my TB app and decided to try using a dark theme. Switching to the built-in dark theme worked as advertised. But installing a theme from the TB UI does not work as expected. Perhaps I'm missing how it's supposed to work, but I can't see how to do anything useful with installed themes.
I open the add-ons manager, select the Themes tab, and enter a search term in the box. This opens a tab where I see some theme add-ons highlighted and available for installation on my version of TB. I select one of those, install it, and restart TB as prompted. Installation was apparently successful, but I don't see the theme listed in the theme manager. It's as if the installation had no effect.
After scratching my head for a while, I happened to notice that the installed themes are listed in the Extensions tab. I'm installing extensions explicitly identified as themes, and I got to them by clicking on a search box with a label "Find more themes", so I think it's reasonable to expect them to show up in the theme manager after installation. But more significantly, I see no way to manage them as themes. In the extension tab, they're either enabled or disabled (or I can remove them), but there's no way to manage them individually. If I've installed and enabled 10 themes, for example, does that mean they're all being combined somehow? Since they don't show up in the theme manager, there's no way to turn individual themes on or off.
Maybe this is a bug, but I didn't find any reference to it in on in-line searches. If it's not a bug, then I'd like to know what the intended CONOP is for using additional themes, because I don't see the point of having a theme manager if any additional themes installed are going to be managed in a different tab. Also, what does it mean to enable a theme in the theme manager, while some number of theme extensions are enabled in the Extensions tab?
I'm using TB 68.3.1 on CentOS 7.7
Alla svar (2)
In general, I never install add-ons from the TB browser, but download the xpi installer and install by drag and drop onto Tools/Add-ons/Extensions, or clicking the gear icon next to search in the Add-ons manager, Install Add-on from File..., select the xpi.
Starting from this page, and right-clicking the Download Now button, Save Link as..., downloading the xpi, and installing as above, I find the themes listed separately in Tools/Add-ons/Themes (see picture).
I can't explain why your method doesn't seem to work, but I put it down to poor design.
The problem seems to be that the internal search from within TB points to a page which has theme extensions that work as I described. That's true whether I install them by clicking the link or downloading the file. Files downloaded from the site you linked work properly for me, as they did for you.
I can get to the site you linked from within TB if I explicitly click the THEMES button at the top of the page after searching for themes. When the page loads, the toolbar at the top has buttons EXTENSIONS, THEMES, COLLECTIONS, and MORE.... Neither one is highlighted or otherwise indicated to be the current selection. And since I clicked "Find more themes" to get there, I didn't think to click the THEMES button. Paradoxically, after clicking THEMES, the text "Featured Extensions" appears at the top of the results, while before clicking that, when I was apparently looking at a list of Extensions results, no such label appeared.
So I agree there seems to be a poor design, but it's the addons web page, not TB itself that is poorly designed. I don't understand why there are things identified as themes that are actually extensions. But sending users to such a site by default when they search for themes, and giving them no visual indicator that they were actually directed to an extensions site, compounds the problem.