Ax+B is industry standard name for that function. With uppercase A and B and lower case x
Please, check other operators on the DHO800 (A+B, A-B, A||B, etc.): all other operators show A and B as actual captured waveforms, but in the operator "AX+B" letters A and B represent the numeric constants.
So, to prevent confusion, either the mentioned operator should be renamed, or all the other.
PS: I would prefer mathematical conventions: "x y" - for the waveforms, and "a b c" - for the constants.