Hi,
this question has some overlap with Modifying an existing column in RDataFrame, you might want to check that out.
The short answer is that, in RDF, the way of expressing that 11_presel has a value that depends on the other columns (through the “check of other conditions” that you mention) is to explicitly write that dependency down as the Define expression.
The biggest issue is that besides what happens in the Define expression, you have no hook into the event loop: you can’t do things in-between RDF event processing.
Cheers,
Enrico