device bank 3rdP plugin on/off parameters

Has anybody else run into this issue?

I have been configuring my plugins to work with my endless encoder controller and can't seem to get the encoders to work with plugin on/off or stepped parameters (anything with a dropdown menu on the ableton plugin configuration page). They work when I map the plugin to macros, but that way I'm limited to 16 macros. The workaround has run into a brick wall though, since some plugins have way too many buttons.

How can I get my endless encoder to trigger stepped plugin parameters on 3rd party plugins?