I was tought this on the 744 back in '98 it's certainly not new and figured any Boeing with FLCH had it.
It's in the 744 FCOM 1.
Autoflight > Controls & Indicators > Mode Control Panel (MCP) > Flight Level Change (FLCH) Switch.
AFDS attempts to reach MCP altitude within 2 minutes using available thrust. Otherwise the A/T uses CLB or IDLE thrust to reach the MCP selected altitude.
And it's in exactly the same place in the 777 FCOM.