The %mac for T/O from the trim sheet provides an almost zero stick pressure for the N1-out climb after clean up. Thus, the pressure on the control should not be trimmed during intitial climb.
Cleaning up the aircraft, on a normal all-engine climb, will also reduce the pressure to almost zero.
The change in %mac during cruise, i.e. fuel burn-off, is calculated by the FMC and shows up in the changing values.
There is no procedure and no need for any pilot input once the aircraft is airborne. As a matter of fact, changing the trim figures in the FMC to a higher value will reduce the amber g-load protection bar and allows the computer to operate at a higher IAS / Mach number; a very dangerous idea as it has been seen several times, unprofessional and total lack of understanding of the system.
The trim indicator beside the trim wheels, as mentioned before, are rarely matching each other, and are used only to set the appropriate T/O trim setting; inflight this indication can be used as an idea about the trim situation, but, as one can read on the scale, it is only valid for T/O.
On a CAT II/III approach, after the auto-trim action, settings of up to 7 units can be observed, well outside the green band. As said, this value is only for T/O, it does not provide any valid figure for landing.