Correct me if I'm wrong, but it sounds like you want two delay settings: short slapback delay and longer delays. You want to be able to switch between the two and have the given effect stay on when you change presets. You want both delays to be ducked as well. What you want to do is have two presets in the same bank, both ducked delays. Set one (say, delay 1 within the bank) of them to have a shorter delay time (your slapback sound) and the other to (say, delay 2 in the same bank) to have your longer delay sound. Then, in the global settings, make sure you have the bypass set to DSP + FX. That should do what you want it to.