If you need to keep cover of pan or bowl slightly opened during cooking, what's the best way to do this. May be there is devices for that, if so preferably non-metal. Specifically glass bowl like Pyrex in a microwave.
Tilt the lid.
It will stay where you put it… approximately.
See pan top left & pyrex bottom right; they will stay like that all day if needed
If it really refuses to stay, then wedge a spatula [or any other bit of wood or plastic (& of course, not metal if it's going in the microwave) of any appropriate size]* in it, either from the edge, down the handle, as at bottom left, or right the way across then balance the lid on top of that, as at top right. The latter will also go in a microwave.
*This is physics 101 - put something in that's big enough to hold the lid ajar, yet not big enough to get in the way of anything else & not small enough to fall in & get lost in whatever you're cooking…
Funny enough, I saw a little silicone gadget the other day when I was out shopping - those stick men called Lid Sid are designed to do exactly what you want. Granted, they are real unitaskers, but also kind of fun.
Other manufacturers make similar items in other shapes - I have seen sheep, witches and others.
If you were doing this a lot it might be worth making a little thing with an H shaped cross section (like a bit of a girder), one pair of legs straddle the rim of the pan and the lid rests on the others. You could make it asymmetric to get variable heights. You'd have to consider the material carefully, i.e. no metal if it's to go in a microwave, some woods & plastics are more heat resistant than others.