Originally Posted by
chacor
No security if transiting T4 to T4S. You arrive into the T4 departures area (since it's all within Schengen). Look for signs to gates M & S, which should take you to the train. After the train, you'll clear outbound immigration. I would suggest there's little time for the Velázquez lounge indeed.
Agreed. A 65min connection from T4 to T4S after a long taxi from the runway, and a missed train means probably no time at the lounge before heading to the gate for boarding. By no means a rush, but also by no means a rum and coke in the lounge.