One immediate suggestion for improvement: if you open a folder, then open an app, the folder sub-app disappears. This is good, and 'correct' behaviour. However if you swipe the sub-app away to get back to the main app screen then it doesn't disappear but remains in the background. Indeed, if you open the sub-app again there will be two of the same sub-apps open in the background! You can potentially open an unlimited number.

Also, if you swipe the sub-app down to close it on purpose, it does close, but you are left in the open-app view instead of back at the main app screen.

The best solution would be for the sub-apps to check whenever they are in the background, and close themselves if so. They basically should never be open and in the background.

There is also a slight delay when opening the sub-app 'folders'. Any way to speed this up?