Thanks Hans-Oto for the quick reply. I also found measurements of spores, unfortunately there are not enough measurements, maybe it will be enough. Even the first ITS research: 
2024-3052-ALV48470 3-16/9/2024 * = ITS ok, 99.83% undetermined
Helotiales MZ650953, 98% Zalerion, Helicodendron, Halenospora and
others, LSU?

In the water

The paraphysis is dead but remnants of the refractive vacuoles (VBs) are visible.
Actually I see a 100% match between MZ650953 and
KC411993 Hymenoscyphus imberbis strain HB 6797 from Tübingen.
This was a typical representative f that species collected by me. So your specimen is also H. imberbis.
An unpublished LSU of H. imberbis (HB 7894 from Mongolia, without ITS) is 99.8% to L. tubulosa (e.g. CBS 125202), Centrospora clavata, Tricladium obesum and Spirosphaera floriformis. But in ITS blast of my H. imberbis I get only Tricladium obesum with 97.5% and Lambertella tubulosa with 97%. So these are obviously not conspecific and LSU is not useful for species delimitation.

Thank you for the comprehensive and supported answer
Greetings from Slovenia
Bojan