I think it would be better to give, e.g. 'delete from this grid' number 2 always and 'delete from this parents' number 3 always, rather than promote 'delete from parent' to number 2 when the item is not assigned to the current grid. Hence, in that case, there would be no number 2. Then users could memorize the number for what they want to do and confirm the dialog without having to check what's what beforehand. Alternatively, maybe assign additional letter-based shortcuts, e.g. 'p' for 'delete from parent etc.

 

Cheers