Because of the way that GC is designed, the forum list select input when moving topics is only going to give you the option to move it to other forums that are in the same collab context as the one you are moving the topic from. This creates a bit of a challenge when you have the need to move a topic from outside a collab into a forum inside a collab, or between forums from two different collabs.
Luckily, this can be done pretty easily with the use of an automation rule:
Rule: Move topic to a specific forum id
- Event: Custom data updated: New Forum ID
- Number Value (Forum ID is not zero)
- Move topic to new forums (Move topic to new forum)
- Update custom data: New Forum ID (Set forum move ID back to zero)
With this rule, you simply need to EDIT the first post of a topic and enter the ID of the forum which you want to move the topic to. The rule will take care of the rest.