Variable cruising altitude ?

Hello,

Can we use variable cruising altitudes in our flight plans ?

When I fly in mountains with an Icon A5 at low altitude, I follow ground level.
User waypoints can be too low, too high,I cannot read some of them while flying, just because my cruising altitude varies !

Here is a .pln alt sample :
<CruisingAlt>4000</CruisingAlt>

Is there any tip  ?

Thanks.