Is there a way...

[Eodin]

Is there a way, other than Compound Power, to set up a power in Hero Designer so that Reduced END only applies to part of the power? Probably not, but I thought I'd ask in case I'm overlooking something.

Old way: Firebolt...RKA2d6, Reduced Endurance (0 END; +1/2), Reduced END only affects last 1d6 (-?)

or as a compound power
Firebolt: RKA 1d6 plus RKA 1d6, Reduced Endurance (0 END; +1/2);

[Simon]

The "old way" that you have listed is invalid and does not yield proper math results.

Compound Power is the "by the rules" way to do things. Anything else, and you're on your own (with a Custom Modifier).