Ok, I’ll not say that mediabay is not actually good
but anyone tried Soundly which is independent app for searching SFX on your drive or on Cloud ( some from soundlythemself and some from your soundly cloud)
I found it very nice if it is possible to integrate some of these apps to the workspace view of Nuendo
or even if it is possible to add extension system for those kind of tools so it can be easily integrated with Nuendo
Your best bet would be Basehead.
https://baseheadinc.com/index.php/basehead/
Really great integration with Nuendo.
Fredo
I wrote to Peder Jørgensen, the leader programmer of Soundly, and he’s promised that Nuendo integration is on its way. I don’t know about “spot to track” and other useful staff, but hoping there’are will be as well. Also this kind man gave me 6 months free promo code! The most nice support, you know 
I have both Soundly and Basehead and have to say that both are pretty good with speed of searching. Basehead has great functionality for sophisticated sound design and higher price .Soundly has nice cloud library in pro version, a little bit easier folder navigation and is completely enough for simple sound design.