BLANK input form wtih all zeroes at Most granular level ( all dimensions drilled down).

How can I create a new input form for Plan, with all Zeroes at most granular level.
Like shown below. When I create a plan version by copying actual, I get non editable cells. I want all cellS in form to be editable and have ZERO value in them when we start. User want's the ability to enter plan data at any/all levels.