Since a while, the first virtual copy is called “master” and can’t be deleted anymore for unknown reasons.
In earlier versions of Photolab, each version was of the same value. There was no “master”. And of course, any virtual copy, including the first one, could be deleted.
The current behavior is a setback, an unnecessary limitation.
I use virtual copies to investigate different approaches, compare them and select the best. The other variants are then useless (“bad”) and shall be deleted.
Why should the first incarnation be treated differently from the other “copies”?
Therefore I ask DxO to restore the ability to delete any copy, including the first one (now called “master”). This could be achieved also by being able to switch the “master” property among the virtual copies anytime.
To be honest, I would prefer to handle this as a bug but maybe this issue gets more attention as a feature request.
P.S.: This has been already mentioned 2020-02 in Set virtual copy as master - #2 by mwsilvers but not as a feature request. Other posters considered the current behavior as a regression.