When I started making maps sometime earlier this year, they were in the vanilla Doom format. Only recently I discovered the possibilities that new formats such as UDMF offer. So I decided to convert my existing maps to this format.
It wasn't as easy as I thought. I tried several conversion tools, but some of them didn't convert the action specials (switches, traps etc) correctly, while others didn't work at all. Took me a while to figure out how to do it, and the process involved several steps with the command-line programs zwadconv, wad2udmf and zdbsp.
To make the conversion process easier, I created a little tool which combines all these tools into one, similar to a front-end program. You just select a WAD file, let it convert, type a new name and that's it.
It converts any vanilla Doom/Doom2 or Boom-compatible map to UDMF.
ZDoom forum development thread: