Here's a constrained notched plate, something like yours, that contains five notches. Number of notches is fixed, as is the number of circular holes and the general shape of the entity. The eleven dimensions shown are fully constrained, meaning that changing a value in the Calculator Palette will result in an immediate update of the 3D object. (A radical or unreasonable change might well screw the thing up irretrievably -- and it's the TCad Genie who decides what's radical or unreasonable.)
I've attached the .tcw file, in 32-bit v19 format, for what it's worth. Frankly, I think you'll find it isn't worth much at all, since the Constraints in any nontrivial drawing are just about impossible to untangle. This one contains 222 Constraint "Block Marks."