In the new version, if you try to copy-paste or insert game data the "next" button is greyed out.

In the old version, it claims to insert the data but when you actually put it into the game none of it works.

The only solution right now is to use the new version, pretend you have a blank bitsy game... and then rename every tile, and every mention of that tile on the room map, to a new name by hand, to avoid naming conflicts with your existing bitsy data, before you copy-paste it into your game.