morganok.... I have this dream #FreeCAD workbench to simplify one of my most common workflows, flat pack plywood construction. The issue is designing slot/tab at the sketch level is a pain, especially when making major changes like changing stock thickness and variable stock thickness (narrow finger, thick slot). My goal is to use #Assembly4 LCS points to set locations and have the WB generate slots and finger. Brain dump here. https://git.oit.cloud/morgan/Plywood_WB
Chris Huck 
@morgan This sounds a lot like sketch driven patterns in SolidWorks. Define points in a sketch at each place that you want an instance. Then, procedurally generate your tab or slot at every point in the sketch. You would have to have a thickness parameter defined somewhere to reference, much like with sheet metal.
@chrishuck Yeah, that's along the lines I'm thinking. There will be variable definitions for sure, but I'm also thinking (hoping?) thicknesses can be pull from the Z of a primary Pad, or possibly Bounding Box. All speculation now, starting setting up the basic WB last night, going to be a lot of App::Link experimentation in the coming days.