You may encounter the situation for modeling fillet in Revit, when changing the controlled parameters' value, the fillet may be disabled. Here are several methods that will control the different types of fillets.
In this case, we need to rely on below several parameters to control the fillet. Shown as:
And below formulas also need to be added,
Length=Sqrt(2) * t
R= Length / (2 * cos(45°+Angle))
I.e. we should label both the radius and the chord length.
And below formulas should be added,
Length1= 2 * R1 * cos((90° + Angle) / 2)
Length2= 2 * R2 * cos((90° + Angle) / 2)