I don't think a key binding option exists for individual plug-in bypass in the FX bin ...
If it is a ProChannel module you can ACT map the on/off button and bypass this way (you could try this with FX bin plugs as well but I'm not sure if it will work satisfactory because there are reported issues with ACT mappings of certain VST3 plugs) ...
This actually relates to a feature request I posted because I miss basically anything that relates to key bindings of ProChannel functionality (insert, replace, delete modules, ...)
My feature request from a few weeks ago:
http://forum.cakewalk.com/FindPost/3187377