You could put in the duration time of action x and make another USQL for action Y. You could also mark the requests as Key request and formulate a chart off of that or even conversion goals
I need a metric not the sum of two steps, but the duration of the period in the session between two steps.
we have a metric for the duration of the session. So I need only part of this metric regarding the two steps of the user in the funnel
No the only place this is available to any extent is if you're looking at a single user's session where you can see all of the user actions in order but there's no way to get this as a metric or even as number from usql.
With usql you can get start times and end times by querying the user action table but you'd be querying both relevant user actions you can't have data from both of them in the same row. And if you queried from the usersession table you can pull from the useractions but you can't get the starttime from two actions separately, there's just no way to express that.
You'd need to be able to do something like select action1.startTime - action2.startTime as difference from usersession which you cannot do.