I've followed this on and off for years, and I've always pined for a mobile version - to the extent I seriously considered learning mobile development in order to write my own!
TreeSheets is written with wxWidgets, which sadly has very disfunctional or even missing mobile ports. Likely you'd want to redo the whole UI anyway for this to function on a phone screen.
Then there's the matter of file storage.. it would need to hook up to some kind of cloud account etc.
In all, the amount of effort to bring this to mobile might possibly be the same as writing it from scratch.
