Since I updated to v4.4.4 today, ABRP predicts consumption with the trailer profile as well as without trailer. The profiles are calibrated using an ODB dongle. Reference consumptions of the profiles are within the usual range.
In the meantime I learned, that the problem is that it takes a long time from switching between the profiles until the chosen profile is fully used for planning. Actually, I switched the profile four hours ago and it still plans with the consumption of the other profile. Normally - since I opened this ticket - it took only 5-30 minutes. Before it took only up to 1 minute.