Lateral Revision and type in the next waypoint may be quicker than clearing.
Having the original route in the secondary can be useful if you get cleared to a way point you thought didn't apply anymore.
Remember you can't activate the Secondary Flight Plan in NAV without going into heading first, unless it is sequenced with the active. Direct To will stop the sequencing of the secondary.
Extending the centreline and having NAV armed whilst in heading will prevent you from flying through your final course and possibly infringing on a parallel runway. I do this if cleared for ILS approach whilst outside the 25nm protected area.
The FMS is a tool box and there are differences in how people use it.