Apple - Move Window by clicking on any part (as on Linux)?
You can use the free utility called "Easy Move+Resize", which allows you to use Cmd + Ctrl + Left click anywhere inside a window to move it. The modifier keys can be customized so that you can choose for example Alt + Left click instead.
You can download the utility from here:
https://github.com/dmarcotte/easy-move-resize
Read under the heading "Installation".
If you have High Sierra or later you can do this natively with macOS, no 3rd party app required:
Run this command in terminal to enable Ctrl + Cmd + Click in any window to move. Restart after.
# to add
defaults write -g NSWindowShouldDragOnGesture -bool true
Run this command in terminal to remove this functionality. Restart after.
# to remove
defaults delete -g NSWindowShouldDragOnGesture
sourced from http://www.mackungfu.org/UsabilityhackClickdraganywhereinmacOSwindowstomovethem