In Thunderbird 78 you can find the settings / options in the "Tools" menu → "Add-on Options".
This is the result of the technology used (WindowListener API) in the associated Add-on version. The Add-on behaves exactly as one was "used" to do with Thunderbird 68. Incidentally, this applies to all Add-ons that have been made compatible with Thunderbird 78 using the WindowListener API.
From up Thunderbird 91 will the options of this (and all other) add-on(s) be accessible via the Add-on Manager, which is the result of the new MailExtension API. In Thunderbird 78 there will be a "mix" in Tools menu and in Add-on Manager.
QuoteColors could look like this in Thunderbird 91 in Add-ons Manager options:
https://www.thunderbird-mail.de/attachment/155…-clipboard-png/
I just installed version 2.0.7 of Quote Colors and now I do not have an entry for Quote Colors in Tools > Add-on Options like I used to. Has it moved somewhere. I looked around but couldn't find it anywhere. In the notes it says "This addons options dialog has now to be opened from the Addons Manager Tab (because of the internal WindowListener-API update).", but I do not see Options as a link anywhere on the extensions page in the Addons Manager.
Thanks,
Bill
I finally found Options in the ... menu to the right of the disable/enable slider. Don't know what made me look there. I have never seen options there for any other extension. Usually I see them in Tools > Add-on Options or as a separate item in the Tools list or as another item on the line that usually has Details and Permissions in the Addons Manager entry for the extension.
In any case, I did find it. Whatever is the correct place to put the Options... I wish extension writers would be consistent in how they do it. It is confusing having 4 different places where they are put.
Thanks!
Bil
It is confusing having 4 different places where they are put.
This is on the one hand the result of deliberate changes by the Firefox (and thus also Thunderbird) developers and on the other hand the result of the WindowListener API used. This WindowListener API helps us add-on developers to make older add-ons for Thunderbird 78 and 91 easier to run. The API mentioned had taken over the add-on settings menu (in the extras menu) from Thunderbird 68 for Thunderbird 78 as well. Strictly speaking, this was a mistake that had already led to inconsistencies there. The API has now corrected this, so that the settings of my "old" add-ons, for example, can now be found in a different location to the amazement of users. See the screenshot: RE: Allow HTML Temp - Version 6.0 für Thunderbird 78
In Thunderbird 91 it will look different again. See this screenshot: RE: Allow HTML Temp - Version 7.0 für Thunderbird 91
Thanks for the explanation. That does help to explain it. A question though... what is the extras menu?
I don't mind the location changing... as long as I know where to look. 
I just hope all add-on developers stick to the same location!
Thanks,
Bill
what is the extras menu?
Sorry, in english Thunderbird versions it is the "Tools" menu, which is translated as "Extras" in german Thunderbird.
Do we have an English support article (URL?) on SuMo explaining the different places to open addons options? Maybe this article could/should explain the "problem" with the changed WL API behavior, too.
Explanation in addon developer support group:
https://thunderbird.topicbox.com/groups/addons/…bootstraploader
Linked from within Thunderbird:
https://support.mozilla.org/en-US/kb/thund…nfigure-add-ons
That page did mention the "Extra/Tools" location until a few weeks back, but was cleaned up after the WL was updated.
