If you know the math behind involutes, you can create template parts reasonably easily that you can reuse or import into new parts. There is some much complexity in gear design, an internal tool would either be overly complicated, or severally limiting (worked as a gear designer for several years). Probably best to leave it up to standalone software that specialise in gears, or create rough “looks pretty” basic geometry parts and leave all the computations on the drawing for manufacturing etc.
Don’t get me wrong, would be an awesome feature, but gears as simple as they look, there is a lot to them, if you are designing custom gears, rarely are you using standard by the book calculations, so the tool needs to be able to compute form modification factors, profile crowning, root modifications. The list goes on. I have a spreadsheet for designing gears that would give people nightmares!
