Board Thread:Suggestions forum/@comment-38580564-20190713005437/@comment-25612015-20190713025554

I made a tool that can do that.

You would place yourself in your Minecraft region files directory and use the command:

RegionScanner --replace b,minecraft:lava,AMBIANT/b,minecraft:flowing_lava,AMBIANT --from path/to/level.dat *.mca

All existing lava would be replaced by the most represented surrounding non-lava blocks (or by whatever block you specify instead of AMBIANT).

You could use a mod such as ChunkGen to pre-generate chunks in region files before using RegionScanner.

I'll probably release the tool this week-end.