Your request is not valid, because if it were, you could not nest tuplets. I understand you want to be more efficient, but you have to understand why what you’re asking for is not what is implemented and why.
Unlike other notation software, Dorico’s tuplets are mathematically perfect. This is why you can use them without problems to “fake” perfectly synchronous meters (12/8 vs 4/4 or 3/4 on independent meters) or nest complicated tuplets. Nevertheless, some optmization has been made : if you invoke the tuplets popover and type 3, you’ll get a triplet without having to input the whole 3:2 of 3:2e.
You can use macros if you need something more complicated.
Hope it helps!