How can I configure Atom to use a Control+Space hotkey to highlight, like Emacs?
I’m not sure what you mean by highlight? Do you mean select text?
Yes, that is correct.
Can you elaborate more? Do you mean the cursor is at
X, Y and you press Ctrl+Space then move the cursor someplace else and press Ctrl+Space to mark an area?
If so, you might want to take a look at the joe-keybinds package. It has similar functionality a la old Wordstar-like ^K^B and ^K^K keybindings to mark a selection region. You could use it as a basis.
Good thinking. Hopefully emacs-plus does the trick!