I've uploaded the map editor for EUO Boomer Shooter, which is actually just the map editor for EUO but with the dat files tidied up to make it slightly easier to use.

Extract the files into your boomer shooter directory, and if you did it correctly there should be a maped.exe, some new files in the dat directory, a new pics directory and a file called monsters.txt (alongside monsters2.txt) in the sdat directory.

Maped is very old and the interface is a bit fruity. Here are some links about how to use it:

euo manual: https://euotopia.com/manual/index.php/Maped_Introduction
forums post about maped: https://forums.swut.net/viewtopic.php?t=3920