You can post here in the forums. If you have many requests, you can post multiple in a single thread. If accepted, the requests get promoted to the editor Trello board. Please search there before posting to make sure your request is not yet there.
Right now the highest priority for Spin development is editor stability, skinning, and updating the runtimes for meshes, FFD, and skinning. No other major features will be added until that is done. If a feature request is easy to do we can usually squeeze it in, but large or complex changes will have to wait.
I added the fullscreen button in 1.8.15.
