At the moment, the easiest work-around is probably to make a Channel Strip Setting for each favourite plugin, and load them from the Library tab.
You can customize your Library file structure by dragging around your .cst (Channel Strip) files in the Finder, making sub-folders, etc.:
/Users/~/Library/Application Support/Logic/Channel Strip Settings/Instrument(or Bus, or whatever plugin type)
How do you use this method for anything other than the first insert in the chain? Seems no matter what, you lose your existing plugins in the chain when loading channel strips from the Library, which makes this approach moot to me. Did I miss something?
You could cram one Channel Strip Setting with your 6 or 8 favourite plugins, load it when you need any of them, and then drag the ones you want at that moment to your working track.
I know, not really what you wanted. :^( But maybe this strategy could be useful at some point.