Floating parquet transition tiles

There is also underfloor heating...

That would not be a problem even with a screwed connection (with dowels).
On the one hand, the heating elements are at least 40mm below the top edge of the screed, and on the other hand, one will always first determine the position of the heating elements with a suitable testing device (or if available: with a thermal imaging camera).
Otherwise, bonding the base profile is actually a safe option!

Thank you very much for the detailed answers!

: Have you attached a profile in the meantime? At the beginning, I also didn't have any rails installed. I had an expansion joint between parquet - parquet. The whole thing, as with you, is always a bit cushioned. We once had it filled with silicone, but in the end, the joint also cracked and it didn't look nice. In the end, I bought a transition profile to glue on. It has only been installed for a few days, but it was easy to attach without much drilling, and so far it is holding. Presumably, a screwed-on part is better and more durable, but I am satisfied with the self-adhesive variant so far. We also had the transitions between tiles - parquet filled with silicone, and that has held up very well so far. This is probably because the tiles in that area do not move and are rigid.