Thanks! I kept thinking it would be under Acquire.
And that would not be wrong thinking.
Upper models do have additional acquisition modes ERES (Hires of a sort) and Average as acquisition mode, in addition to have it as a math mode.
Advantage is it is a bit faster, but if you use it as acquisition mode, then it applies to all channels and you have no original waveform.
When you apply ERES or Average as math, you can it individually on each channel, and you have original data too.
So even when scope is stopped, you can, for instance, change ERES parameters post stop to tune in best result.
In practice, I use ERES and Average as math channel most of the time, even on scopes that support it as acquisition mode, because of those reasons.