I think the amount of variables you would like to tweak is exactly what saved workflows are for. I do not know the issues you are having but saving workflows has worked for me to lock in place all of the variables you mentioned. I'm not sure why you would want so much flexibility within a single workflow. There are xy-plots for doing some amount of experimentation, but after you've learned what you can from an xy plot, it is good to lock things down to a trusted, predictable workflow. If I want to do some testing with several models in a short period of time, I just open several workflow tabs and switch between them. Or is that redundant?