Would normally post to the Bug Tracker but as it is currently down hoping one of the Fusion devs might see this here.
The one single feature that would have the biggest impact upon making a game over multiple frames would be the ability to create objects from other frames in the Global Event Editor and/or Behavior events. It is possible to do this in the regular frame editor but not the Global or Behaviour events editors.
While creating a game with many frames, you may often want to introduce a new object. Right now, if you add a new object to your game, you have to copy and paste it into all of your frames where you need it and if you have dozens or hundreds of frames this is a chore.
I use global objects and event behaviours quite a lot so I can make changes to existing objects easily but the final irritation is that I cannot create objects unless they have been added to the frame already.
Add a new feature to allow the Create and/or Create by name actions, from the context of Global Events or Behavior Events, to create an object that exists in another frame.
eg: the Create by name action could be written as: "Frame 1=>Fred" - this would create the object named "Fred" that exists in a frame called "Frame 1".
How this would help
I could, either with the Global Event editor or a Global Active object with a behavior, use actions to create all of the objects I need to have in my games frames.
When I want to introduce a new object, I'd create it in one frame and then add a single action to my Global event and all frames that use this would now have the object. No additional work required whether I have 10 frames or 100 frames.
I know your focus is on the next version of Fusion but this new feature would take away a lot of pain in the current version and it would really help.