Check explain plan of a running query in other session

Hello,

I am asking myself for a while if there is an easy option (via dictionary
views like pg_stat_activity or similar) to check what execution plan was
chosen for a long running SQL statement while it is running in a different
session?
I have a performance problem in a plpgsql procedure that executes an update
within a loop. My guess is that it chose a generic plan instead of bind
peeking and then does not use an index.

I am not able to proof my theory, since I don't know how to get the explain
plan for it.
For me the easiest would be to check the running statement in a different
session and "hook into" the other plpgsql session to check what the
optimizer chose.

Is that something I can do easily? If not: What is the PostgreSQL way of
doing it?

Danke und viele Grüße
Jonas