The topic says it all. I cannot find any information on the monodevelop site or through google.
Even adding System.Diagnostics.Debugger.Break() and runn
System.Diagnostics.Debugger.Break()
the soft debugger doesn't yet support System.Diagnostics.Debugger.Break(), so that won't work.
You just need to debug MonoDevelop inside MonoDevelop and set your breakpoints on the source files of your addin.