I just tested this out.
It seems to work fine for me (the button is at the bottom of the extension list for me)
I am sorry you are dealing with this but in the meantime have you tried this:
*Have you tried selecting help in a new project? Does this happen to all projects?
*Have you updated to the most recent GDevelop update?
*Have you close/open GDevelop?
*Have you uninstalled + reinstalled GDevelop?
*Have you updated/restarted your device?
If you have done all these things and the bug still persists, then I hope a moderator can take a look at this.
Are you using the latest version of GDevelop?
I cannot find this button in v154.