Thank you! I’ve been wrestling with this all morning and when I read your post I was like “HECK YEAH!” and also like "How did I not realize this sooner?
For anyone else who finds this and needs more context - I set up a wireguard interface to mullvad using a combination of
https://scholz.ruhr/blog/mullvad-as-second-wan-on-mikrotik/
and a great forum post here about it
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1
these videos helped a bit
2 videos by ‘network berg’ about mullvad on mikrotik
https://www.youtube.com/watch?v=4Z32oOPqCqc&t=1559s
https://www.youtube.com/watch?v=pec1Ku2G2LE
Mikrotik VLAN : Create and Configure ( VLAN, IP, DHCP, NAT ) by NETVN82
https://www.youtube.com/watch?v=3m6AsMdZgOE
But after mashing up all of the above I couldn’t figure out how to whitelist my local devices, specifically the router, on the VLANs which are tied into Mullvad. The comment here, to just add a !DST-Address rule in the mangle was super helpful-I spent all morning trying to figure out how to create a seperate set of routing rules to exempt that traffic.