How do I fix Universal Minecraft Editor's broken chunk locator?

Solution 1:

It was only a minor change that caused the Chunk Locator to break in 1.16.100. This minor change was the moving of the ChunkVersion tag to a different location, from byte 177 to byte 44. See the Minecraft Wiki for source.

Unfortunately, after emailing Matt G (oPryzeLP), he does not plan to fix the software, due to it being unpaid for.

But, all is not lost. I am happy to inform you that after speaking with Tryashtar on the Minecraft Commands Discord server, they have come up with a solution!

They have now rigged up their Image Map editor to, in addition to reading maps of your world, it will also restore the legacy ChunkVersion tag that is required for UMCE to work.

Just click on the Bedrock World button and click on the world you want to open. This will then automatically add back the legacy chunks.

You can get the file here.