Aircraft tail number simulation variable please

In Xplane it has “sim/aircraft/view/acf_tailnum”. Where is the equivalent in
MSFS2020?? I have looked at other vars such as “ATC FLIGHT NUMBER” but this is
not the tail number. Purpose: Home cockpit builder withe-paper screen that
displays the tail number for use on vatsim etc.

Check the SimVar “ATC ID”.

Ah user has to enter tail number, won’t load in from livery.

That’s not necessarily true. It will load in from a livery; atc_id= I think is
the value in the livery. I believe, however, it is overridden if the user
enters a value in the interface before the flight, and that change is
remembered from session to session until the user removes it. What would be
super nice would be a variable size and location on the plane surface based on
the origin of the plane, that can be controlled by the livery, as well as the
font, etc (which can be done), so the ID can be placed anywhere on the plane
at any size and orientation Sort of a sticky thing that slides on the outer
geometry of the plane placed with relation to the origin.