You need to use at least Blender 2.92.

Please upload your blend file.

This error means that your file contains text with invalid characters. Try ensuring that all names in the SMD file contain only Latin/English characters.

Never seen this before, but it looks like a Blender error that multiple add-ons are affected by: https://projects.blender.org/blender/blender/issues/99440

Sorry, got confused. It's a problem with the SMD file. Where did you get it from? Can you upload it somewhere?

That's an issue with the QC file, not the SMD file(s). Try importing the SMDs directly.

It's too complicated to create anything flexible enough to be generally useful, and QC isn't even used in Source 2

Never heard of it. The only reference I can find is a tiny mention on this page here.

If you find out more I can look into it, but it appears to only be supported in Counter-Strike: Global Offensive, which is soon to be replaced by Counter-Strike 2 on the Source 2 engine, so it may not be worth bothering with.

The Source Tools export animations for compiled game models, not Source Filmmaker. The formats have some overlap but clearly not enough.

The Source Tools don't do anything special with either of those UI panels. You should ask for help on a Blender forum.