Ironically, before the addition of the Media Bay, that was exactly how I handled my plug-ins. I made a separate folder for my EQ’s, Comps, Distortion, Filters and Reverbs. When I opened the insert or aux menus, those five folders showed up and I could select what I wanted very quickly. It worked great in Nuendo 1 -3.
By N4, I’d gotten the UAD bundle and found that I couldn’t place those plugs into the separate folders like the others. I assumed it was a mapping issue and didn’t bother pushing it. I figured that would just be a “6th folder.” I never bothered with N5. I went straight to N6 and started programming direct access to my favorite plugs with a one button function via my Euphonix MC Control.
When I saw this post, I decided to try the old folder routine on N5. Sadly, it didn’t work. So your only options will be as described earlier; using Key Commands (which works in the porject window but not in the mixer), going externally to do this with a controller, or you could make a template with all of your favorites preloaded BUT NOT ACTIVATED) in each channel of your mixer. The down side of the last suggestion is a slower opening of new projects because of the additional weight of all those plugs. But the work-around for that is to only pre-load the channels that hyou know will end up using those plugs about 90 - 95% of the time. That will lessen the load considerably.
I know how frustrating it is not being able to work the way you’d like with a product who promoted itself as one that would let you do just that. But there are always work-arounds. I hope you find one that will work for you.