In the takeoff tools I see there is and option to save as default for the tools which is nice. Unfortunately that is not an option for products and items. It's frustrating to have to keep typing in formulas every time I create a new item that should be default. It would also be nice to be able to paste items directly as a child.
Hey Mark! I'll mention this to the team. In the meantime, if the property you are trying to enter formulas into is a custom property, you can set a Default Value of the formula you are entering.

I do have that set for some, But others like markup % I cannot edit.