Allowed VST2 Plug-ins Dialog NOT working in Dorico 4

Tell me in which universe this makes sense? It shows the four VST2 plugins are both allowed AND blocked!

I FINALLY, after clicking the factory reset button on the dialogue got it to show the correct set of plugins and now, does show only plugins on the right in ‘blocked’ for VST2 which is where I want them, but it “took an act of congress” to make this happen. Not until I clicked the ‘Factory Reset’ button did the change take effect. Clicking both the ‘Clear Audio Engine Cache’ and ‘Reset Audio Engine Data’ did NOT reset the VST2 list for block plugins.

Sorry for all the trouble you had and sure it does not make any sense what you experienced.
On the other hand, I have no idea how you could end up in this mess in first place; it is the first time that someone reports a case like this.
Should it happen to you (or anyone else) again (plug-ins both being shown as allowed and blocked), please do Help > Create Diagnostics Report and post the corresponding zip file here.