What is the opposite of “Overridden“

I don't think there's a good single word for what you describe, and your best bet is to turn the sentence around:

The forecast includes all items unless overridden at the store level.

The forecast includes all items except those overridden at the store level.

or even

Items overridden at the store level are not included in the forecast.

In court, an objection that is not "overridden" is, instead, sustained.

In politics, they say uphold ("The Congress upheld the President's veto.") You could use obey, follow, comply with, or observe, but there's a lot to be said for not override.

If there is a proposal that is not overridden, then that proposal is accepted or endorsed.