Pr1SnesLevEd is a modern Prince of Persia 1 for SNES level editor for Windows.
It has its own forum board.
Download: Pr1SnesLevEd_2016-01-01.zip (421KB)
This latest version was released by David on 1 January 2016.
To use it, you'll also need to download a SNES ROM image.
All old versions: