How to load SEM modules in Synthedit?

Not sure what Category they're loaded in if there's a category mentioned in these modules. I'm not sure how old these modules are and what SDK is used.
Another thing is 32-bit vs 64-bit. You didn't really mention the version you're working on yourself.

Normally it works like this:
copy any 3rd party sem or homemade module to:
c:\program files(x86)\common files\synthedit\modules\ (for 32-bit)
c:\program files\common files\synthedit\modules\ (for 64-bit)

These are the default folders as seen in the refresh window.

If a module doesn't load it could have a variety of reasons and some of them can't be solved without altering the source of the module to i.e. work with the newest versions of Synthedit.

Just fyi, the regular installation directories of Synthedit also contain module folders (these are the SynthEdit Stock modules and these folders shouldn't be used to store new modules in) :

C:\Program Files (x86)\SynthEdit\modules

C:\Program Files\SynthEdit\modules

If you can't find them in the common files synthedit folders, the installer may have copied them into these folders.