Hi,
In Rhino 8 (8.16.25028.13002, 2025-01-28) on macOS 14.7 (Sonoma), STP files that were previously inserted as blocks (cf. block settings below), retrigger the STP Import Options to reappear each time Rhino is launched by opening the 3DM file that references the STP files.
In my case, the STP file is an external file that I haven’t altered in any way.
In my opinion, the Import Options shouldn’t reappear unless the external file has changed.
Here are the block settings I’ve used:
Thanks for taking a look.