Maybe I'm misunderstanding your questions. Installed extensions are in the extensions folder.

I forgot to write that I have Ubuntu 22. Where is the folder extensions? You didn't read https://developer.thunderbird.net/add-ons/hello-world-add-on carefully. It says temporary storage. But I can’t find this very place that is mentioned there at the very beginning of the page.

I suggest you take your addon questions to the addon developers list. https://thunderbird.topicbox.com/groups/addons

I would guess that the temporary extension will be part of the cache, but it could also be included in the extensions folder in your profile. However ask the experts. Not the users.

Thank you very much.

No answer. Does anyone know where else I can go?