Wow! I thought I'd never see the day! A one-time post on this board that is NOT "Do my work for me plz send complete solution and documentation to
wokkietokkie@lazybastard.com ASAP kthxbye! ^_^". And not just that, this is precisely the solution I was looking for too.
Thank you Mr Shroomishness who will likely never see this!
I used the SHIFT-V + properties method first to see if it solved the violations. Which it did.
And for those future googlers looking for an even lazier solution, I came up with the following method.
Assume the QFN component is 'U1', and the thermal pad is pin number 33. Not an unreasonable assumption for a QFN-32 with thermal pad.
Use the following query in PCB Filter:
InComponent('U1') AND (IsVia OR (IsPad AND (Name LIKE '*-33')))
Apply filter, and verify that you indeed have now selected the thermal pad and the thermal vias.
Then go to PCB Inspector, and change
Net to whatever value you need,
GND for example.
Hopefully this helps one of those future googlers.