Pushing inner forEach activities to an outer variable

If your variable is of type 'Array', then the 'Append variable' activity can be used inside each foreach iteration to dynamically append new items to the array variable.

Append variable activity - Microsoft Fabric | Microsoft Learn

Afterwards, the array variable (with the data from the foreach activity) will be accessible for subsequent pipeline activities outside of the foreach activity.

I think the Collection functions are useful for accessing the data from the array variable in subsequent steps:

Expressions and functions - Microsoft Fabric | Microsoft Learn

Also other functions and activities can be useful.