I set TAB to the scanner on PC. The problem is there are two Scan modes to choose from in key bindings, HOLD and TOGGLE. I prefer TOGGLE but if I set it to that I still have to hold the TAB key down to keep the scanner up. Is this just another bug in the massive laundry list of defects with this game?

EDIT Sorry, got your question wrong ^^"

Anyway, I've found out that if you press caps lock the scanner stays on until you press it again (this is with standard key bindings).