Ideas are the only topic type available in Ideation categories, but “Question” and “Conversation” topics are still available to select when users are creating topics in Ideation categories. This is a poor UX because users won’t see the Ideation topic they are currently in as an option in the Category drop-down menu on the topic creation page if they happen to switch the topic type from the default Idea to a Question or Conversation.
The ideal setup for Categories is to enable/disable individual topic types through a checkbox/switch module in the Category creation page in Control, and have only the enabled topic types visible in the topic creation page for that Category.
Another option is to introduce another Category type that includes all topic types (Question + Conversation + Ideation) instead of the “Ideation only” or “Discussion/Conversation only” types.
Our use case is a beta user group -- we would create a Category available only to certain custom user roles where Q&A, Conversations, and Ideas could be available in one place.
I would add that these options for topic types should also apply to Groups, not just Categories (probably a separate idea).