If the aircraft doesn't have a cockpit adjustable rudder trim, and just a ground adjustable tab, then the tab is usually adjusted so that no rudder pressure is needed during cruise flight power & IAS.
For clockwise prop as viewed from the cockpit:
If more power is applied while maintaining the same speed then some right rudder will be needed. Similarly, if the speed is reduced for the same power then R rudder will be needed.
If power is reduced with the same speed then L rudder will be needed. If IAS is increased with the same power then L rudder will be needed.
This means that during typical climbs or descents, some additional rudder pressure will be needed. If the plane has a small speed range and low power the change isn't much and the pilot just has to bear with it while it is needed. For aircraft that have a large speed range or significant power it becomes a bit of a pain so a cockpit adjustable trim is usually fitted. Any time that the plane isn't in balance (ie longitudinal axis aligned with the airflow) then the rudder trim should be adjusted to relieve the pilot from holding rudder pedal pressure.