This mod is amazing and i've used it on a lot of very old maps, but one aspect always bothered me: you mention it will increase file size. Why? Shouldn't it remain the same? (or relatively the same). Regardless, it is exceptional, only wish it was button-operated like the "Regenerate Terrain" mod that like yours, similarly regenerates the map surface, albeit a bit differently.

There's some inflation due to the use of a second surface to do the re-generation, but a big part for really old maps is simply that newer maps store more data. Rseding did a good job optimizing the decoratives part which when I first wrote this mod was major contributor (if moving from a no-decoratives map to one with them, it really could make a file much larger at that time).

As for the button - I admit I was lazy, this really was intended to be a one and done mod for use in a map - fix the terrain tearing, remove, carry on with your play.

This mod does the job at removing bitter creep and nuclear scorch marks.

I noticed hat my map went from 4343 kB to 4534 kB. I suppose that it's just because some decoratives are generated.

So this mod uses a second surface to do re-generation, is the new surface deleted after the mod is used?

yes, it generates a second surface with your same seed but slightly tweaked settings (no ores, trees, enemies, cliffs, water, etc.) and clones in the surface for some tiles (e.g. skip replacing water on Nauvis) chunk by chunk. It does delete the surface actually iteratively, every 250 chunks. In an earlier version of the mod I didn't have that and when the map auto-saved it doubled in size, so I take this minor bump to be acceptable :)

Thank you for your detailed answer, this way I know that the mod leaves the save file "clean" and I assume that there is no risk of save file corruption.

I realized that the mod I'm looking for would be yours but would keep the biter creep floor decorative below default-generated biter nests (not those generated by biter expansion).

Maybe the mod could generate the RePainter map with the same original settings, then delete all { "cliff", "tree", "resource", "unit", "unit-spawner", "simple-entity"} on RePainter map before importing the tiles and decoratives to Nauvis, and skipping nauvis tiles with landfill)?

So a few things. the "other settings" are to prevent most of those things from spawning in the first place rather than deleting after generation. The mod has code to optionally regenerate decoratvies and to clean decoratives off concrete/brick/etc and rails, but it doesn't actually copy any decoratives from the new surface - just tiles. Your idea sounds like it could work though it would take longer with the additional loop for decoratives. When I first wrote the mod the biter creep didn't exist so it wasn't something I bothered handling in any specific way