I don’t know if this is a feature or a bug. I added Macro Oscillator 2 from Audible Instruments while using the VCV Rack Pro VST within Reaper, however the module didn’t show up in my Library until I restarted Reaper.
I then tried adding another module, Erica Synths Black Octasource, and the same behavior occurred. The Library pull-down menu that says “Querying for Updates” showed both modules downloading.
The modules appear to work fine once they’re in my rack.