Is it possible to load (and not activate) the approach procedure on a Garmin 1000 or 430?
If you take a look at the manual for the 430 you will see that you can only load one approach at a time.

Turn the large right knob to highlight ‘Load?’ or ‘Activate?’
(approaches only) and press the ENT Key. (‘Load?’ adds the procedure
to the flight plan without immediately using it for navigation
guidance. This allows the pilot to continue navigating the original
flight plan, but keeps the procedure available on the Active Flight
Plan Page for quick activation when needed.)

The 430 only allows one approach to be loaded then subsequently activate because this is the flow of a general IFR flight and the approach is not technically in the flight plan (its just &quot;primed&quot;). You should know the most likely approach based on winds and weather before even departing. Once en-route you may get assigned a different one but either way you can load the likely approach en-route. If you know your transition point you can even select that as your approach start. If you are unsure, VTF (Vectors To Final) is generally safe with a change when needed. Since the approach is somewhat side loaded and not in the actual flight plan, activating it will defeat all other navigation and take you to the chosen IAF (or nearest leg for VTF).
The other reason that the unit is built this way is approaches rarely follow each other in quick succession. There is often a hold in between or possibly more en-route flight, which is why the suspend button is there (and important for missed approaches).
You are likely missing some of the procedural work that occurs on a real IFR flight. Sims are fun to just hop from field to field flying the ILS but that is not the reality of an IFR flight plan so the hardware is not designed for that.

If you are flying X-Plane or the like and using the mouse to tune the G430 then the apparent programming time is much slower than reality as well. I would advise checking out something like this and you will see how much quicker you can really program a 430 when you have tactile knobs.