So this is a little late, but I was trying to do the same thing, and it was difficult to find. This was one of the first answers in google so hopefully this will help someone who comes across this in the future. In order to do this you need to enable “develope mode” by hitting ctrl+p to load up preferences and tick the box. Then go to strength settings. and click the box for “interface shells” here’s the forum link I found the solution to Stacking prints, setting solid layer between color changes now just set the number of bottom layer infill, in the objects process, for the upper part to set how many filled layers are on the base/lower part.