I would like to report what I see as a bug, and you can try it here in the Discourse Meta site (I advise to test in an anonymous window).
If you change the theme in the hamburguer menu to another that isn’t the Minima Dark Theme, you still see the hamburguer menu with the themes, so that you can switch to another theme (or revert to the previous one) if you want.
With the Minima Dark theme, tough, it doesn’t seem possible (the other themes aren’t shown). I had to delete the cookie that store the theme id to make the theme here from meta return to the original one.
Not a bug, but an oversight. The Hamburger Theme Selector is itself a theme component. It has to be included in a parent theme to work. I’ve added it to the Minima Dark theme so the hamburger selector will now appear.
It would be nice if a theme component’s admin page showed you the themes it was installed/not installed in. Having the information be shown in both sides of the relation would help when you have a lot of things installed.
Thanks for the reply and the quick action to solve it. I’ve not marked your reply as solved because this category hasn’t the solved option enabled, but this bug (or better, oversight) was indeed solved.
Thanks for the tip, but I wasn’t logged when I changed the themes, so I couldn’t access the preferences page (of course, I could just log in and access).