Define Default Conversion Values

How can I set the default conversion values in Calibre? I've already got it set up to, by default , convert from epub to PDF. And, a range of other values.
There are numerous variables and screens.

Now, I want to change some of these.

I know it CAN be done, because...I did it once before! :D But, can't seem to find how to do it.

Thanks! :)))