Hello @User, Whenever I try to generate contacts or vias using the device generation menu, I get those errors and the parameters menu does not appear in the first place in order to adjust the dimensions.

It could probably use a bit of a better interface. The contacts in the menu are more like "helper scripts" for drawing contacts rather than actual parameterized devices, so you can't edit them or bring up a parameter window for them. The contact is drawn within the area of the cursor box, so the cursor box must be at least the size of a contact with a single cut (probably the routine should be rewritten to just always draw a single contact centered on the box whether or not the box is large enough).