The steps of one interferogram creation to measure the displacement or DEM production is explained in the following post,
The atmospheric effect should be excluded, subtracted while implementing steps 5 (interferogram formation),
But as details step by step atmospheric correction procedure of one Interferogram, I think it’s not supported by SNAP atm, But I agree with you, it would be very nice in case it could be included.
This only in StaMPS, and TRAIN could be discriminated,