recording sounds with Windows 10/11 muted.

How do I record Computer sounds with Windows volume in 10/11 muted?

That might not be possible (without “special” software).

One solution is to plug-in headphones/earphones and if they are too loud, sick 'em in a drawer. Or plug-in a headphone extension cable with no headphones.

Computer sound services are pretty simple. Play to you and record from you. If you interrupt either of those pathways, it just stops working.

Yes, some special software packages create new sound pathways divorced from regular Windows (or Mac) and those can be handy for live recording. Also, be warned that Skype, Zoom, etc take over your computer sound while they’re working and sometimes after. You can have two competing programs and Zoom will almost always win.