I think what he is saying is that he wants the A/P to hold the A/C altitude BUTbe able change headings( fly the a/c) manually using the yoke. This can’t be done on modern a/p’s. Engaging the a/p engages 2 channels, Vertical (elevators )AND horizontal (ailerons) Basically if you engage the a/p it will engage and hold the current status of the a/c. If you try to manually turn the yoke to steer the a/c, by design, the a/p will disengage due to be overriden by the pilot. The last a/c that I was familiar with that allowed the channels to be engaged seperately was the 737-200. The a/p had 2 selectors, one for elevators & the other for ailerons. Selecting the various modes does what it says. I am not going to go into Control Wheel Steering (CWS). This is no now available on most a/s of late design. Hope this helps
Kev