Save current floor

First of all, English isn't my native language, so I'm using a translator. Sorry about that, but I have no other solution. Since there's currently no way to configure liquid levels (e.g., water or lava), a "save current floor" option would be great.

Let me explain: I'm surely not the first person to create a multi-level map and realize they can't add liquids to the lower levels because they flood completely, even though the map was practically finished. Currently, the only solution is to recreate the entire map from scratch. If it were possible to export just the current floor as a new map, it would be a good temporary solution until they add the option to configure liquid levels.