Serial monitor smaller

I would like to see that we can downsize the serial monitor so that it does not interfere with other open windows.

Why not just use another serial terminal program then you can do as you wish but have more options for capturing the serial output ?

There are lots of free (no adverts) serial terminal programs out there that are almost always superior to the built in version.

Putty is a favourite of many.
Teraterm is one I like.

Because the ide monitor disconnects automatically when you upload a sketch and reconnects after that.