The basic idea is that one would play to indicate the pulse (it could be nothing more that taps on a keyboard) and the tempo would be extracted and mapped to the bars and beats. Taking it further, one could play a section of the score (perhaps a bar or two with a colla voce, or a rit. and an a tempo, maybe a guitar solo or anything else with rubato) and Dorico would map the played rhythm to the notation. One would be able to edit the mapping manually. The ‘conducting’ could conceivably be extracted from a recording but there’d essentially be no difference.
Have a look at these two threads:
Create a tempo track based on an existing recording - Dorico - Steinberg Forums
Tap tempo - Dorico - Steinberg Forums
Daniel said it was something they intended to work on in future.