Personal Comments and Observations
The more reliable way to ensure cruising altitude is understood by ATC is to file a plan less Departure and Arrivals through an external EFB like Little Nav Map. Save it as a .PLN file, load it into the World Map in the sim. Once in the cockpit, it’s already in the FMS, receive ATIS and dial in a SID if desired (ATC really doesn’t understand SIDs and STARs anyway, and can’t assign it to you).
It’s not as rote as actually plugging it into the FMS by hand, but it does guarantee that ATC understands your planned cruising altitude and step-climbs you accordingly. Those step climbs may not be in 10,000’ increments. I don’t think you can interrupt the ATC flow to request a custom step climb until you’ve reached your original cruising altitude. Usually within 200’ of the last assigned step climb, ATC will tell you to keep climbing until you reach ENR height.
As far as descents, ATC’s gotten better, but you could still be plus or minus 10 nm of a calculated TOD based on an EFB plan export. I personally follow my own out-of-sim plan TOD, using the Vertical Situation Display in my EFB, I make note of the waypoints remaining as a rough altitude request value and start requesting descents to those heights manually from ATC. During that time, you’ll likely get assigned your Approach and you can do the negotiation round or accept.
Regardless of whether you pick a STAR, you will always reach an interim altitude either at or just above IAF altitude constraint, and ATC will nag you to go higher until you reach the magic distance threshold from the IAF. At that point the descent instruction timing and altitude will start to align again with the charts (more or less) and you can fly the Approach to the threshold.