catch big changes in average visit duration

[hpvd]

couldn't find a possibility to catch big changes in in average visit duration.
Is it already available?

Would be good to get alerts for problems as found manually by coincidence and described here:
matomo-org/matomo#9504

[hpvd]

maybe it's this one, but I don't get how to use/fill the fields.
For lessons learned from this see #26 and #25

the other point:
is it about the average? the word average is not visible - hmmm

on other places this is very clear: