Hi JBuck,
great to hear that you're enjoying the sound of MIR 3D! :-)
I agree that it's using two hosts in parallel (Cubase + VE Pro) complicates things a bit. I also agree that a "Search ..."-bar in MIR's instrument list would be a meaningful addition; I'll add it to the constantly growing list of suggested new features.
I have a few suggestions for you, however. I'll attach screenshots to this message with a few markers, numbered from 1 to 5.
#1 and #3: Actually, there already _is_ an option for narrowing the list of instruments, in VE Pro as well as in MIR 3D. Even on the small screen of my MacBook Air I can see around 40 channels/instruments at once like that.
#2 is the plug-in's Focus-button you were mentioning. You will instantly have the respective Icon selected in the Venue Map, and it will be shown in the Instrument Panel, too, as soon as you activate "Follow Selection" (#4) in MIR's Venue Map Controls.
#5 is the little-known "Find in Venue Map" button that helps to keep track in large arrangements, even when zoomed-in all the way.
... maybe you found something there that will make your life easier. :-)
Kind regards,
/Dietz - Vienna Symphonic Library