I don't know that there's a lot of programs available for patch editing on the MT-32, but the two posted on the Utilities Page HERE
are probably the most popular. The link to the L/A Synth Editor isn't currently working, but the link to the website that hosts the software (Ginosoft), is. That, and DR.T's Editor are the most common, and both are good. I don't think any MT-32 editor can be considered "easy" to use, though.