which harp technique is this?

Hello, I wonder which harp technique this is and how to replicate it in Dorico (the „Z“ like at the top of the chords).

I could not find anything similar here: https://w3c.github.io/smufl/gitbook/tables/harp-techniques.html

It looks as an accent AND a tenuto (granted, a little bit too close), more than a Z to me… But maybe I’m wrong and this is a specific marking.

My first instinct tells it might be
striking the strings/chords with both hands in opposite direction.
This could be nonsense though.

I would agree. What score is that from?

It is from L’ultimo canzone by Tosti (1905).

I love this aria, which I have sung many times — but in piano-vocal version. In that piano version, there are accents on the ascending voicing of the chord on “se ti fai sposa”, which could be an indication of the accented meaning of your score, if it’s the same location in the song.

I’m going out on a limb here – I don’t think a Tosti setting will feature any kind of harp “techniques” beyond the ones so obvious that they wouldn’t even be notated most of the time.

Alexander, this is a later arrangement and someone is trying to „recover“ an original orchestra setting from this. The piece is well known in the piano settings, as Marc pointed out.
There are also normal accents in the score for the harp, like here:

FWIW, I just asked a friend of mine (who happens to play the harp at the Paris opera house), he thinks these are the accents I’ve mentioned in my first answer. He has never seen a specific notation for the harp that looks like that.
Hope it helps!

It looks like an early orchestration (1930s vintage) is published by Kalmus, but a online quick search turned up a full set of parts not just the score, which was (not surprisingly) not cheap. It might be worth searching a bit harder.

Rob, exactly. A colleague tries to restore a possible original orchestration by Tosti himself (1905), using the different piano voice versions (which are mostly in D Minor) and comparing them with that later orchestra arrangement (probably a lot later than 1930). So no Glockenspiel, no bass clarinet etc. A sort of slimmed down romantic orchestra à la Donizetti/Bellini.