Unfortunately, that's not always the case; I am currently seeing altitude errors in flight plans produced by Simbrief.
Specifically, constraint altitudes not being set for STAR entry points (so incorrect entry altitude & descent steps), and cruise levels above airway limits.
Granted, and as I said in some post a month ago, If there any constraints to be respected (and Simbrief doesn't) that's on us to correct them when loading them in to PF3. Actually I did have the problem with Simbrief with the flight EHAM-EDDF where cruise altitude was set to FL390. After loading it in Little Navmap it complaint it couldn't calculate the TOC and TOD because TOD should be before TOC. And that is on me to correct in PF3.
My point is that it's not for PF3 nor the responsibility to correct FL in a flight plan when it is specified that SID and STAR will be flown.
which will then correctly apply constraints
Could you please tell me how to do this, I mean for LNM to apply the constraints?
I use to do that too, making my flight plan in LNM and export it to SImbrief, re-import it to LNM and the export to MSFS format.
But I did that because of the AIRAC discrepancy between LNM and Simbrief. But at your suggestion (I think) I did get a month subscription to Navigraph so now I have all my AIRAC synchronized to the latest one. So now I make the FP directly in Simbrief. I only load it in LNM to follow my flight.
That's also the reason why I automatically download the FP both with and without the PROC so I can load the NoProc in PF3 and the full one in to LNM.
I will try out the "filter option" one of these day to see how it goes.
Cheers,
Luc