You will have to put in the time signatures in each bar so that Dorico knows what the beat grouping should be, but you can do it using an interchangeable time signature so that each successive time signature will automatically be hidden – though you will see two instances of 5/4 at the start, so you have to trade these things off against each other.
To create an interchangeable time signature at the start, in the Shift+M popover type:
[2+3]/4 + [3+2]/4
and hit Return. Then create a new [2+3]/4 or [3+2]/4 time signature in each bar as needed, and Dorico will hide them automatically.
It’s also worth saying that you don’t have to add the time signatures up-front: Dorico will update the rhythmic grouping of each bar if you create a time signature after the fact, so you can happily work entirely in e.g. [3+2]/4 and then go back and add the other time signatures as needed later on.