Dear dodoo,
Currently there is no easy way to perform this task. There are some approaches, but none of them is a good idea to use:
- Since versions are not synced from remote databases, you can delete your current database and re-sync it. NOT a good idea.
- You can open the developer console and execute a database compactation. This will erase all historic versions of all tiddlers. Maybe not what you want.
Regards.