Jose wrote
This makes no sense to me.

Yes Jose, we do understand that a lot of things make no sense to
you.

If the airplane attitude remains "where desired"
(I presume that is the same as where you put it, using
pressure) when you release the pressure, then the pressure isn't
doing anything. How do you fly such an aircraft?

First.....Put the nose where desired and feel pressure on the yoke.
Second....Start trimming, airliners generally use electric trim.
Third.....Stop trimming....release pressure on yoke
Fourth....Check nose position, if it stays where you put it, you
did the correct amount of trimming, if not, repeat the
procedure as many times as required.
Fifth.....If all else fails, turn on the autopilot and let it trim.

Actually, on the older Boeings that I flew, the pilot could do a
better job of trimming than the autopilot since the autopilot did
not mind holding a little pressure forever. Only when the elevator
became some number of units out of alignment with the stabilizer did
the autopilot kick in the stabilizer trim system. It was common that
when flying on autopilot,if a pilot observed on the control surface
deflection indicators that the autopilot was actually holding some
'up' elevator, he would use the manual trim wheel to fair the elevator
and stabilizer and reduce the 'trim drag' which could consume a lot of
fuel.

Bob Moore