How to refer to previous step in Custom Function when it is in subtable

[DSR]

Hello, your help please,

in creating and using the Custom Function the PreviousStep is "Col.IndexSub" which is inside "FullTable" I want to access it when invoking the Function on the left, but the box shows queries outside.

 

[DSR]

 

 

[lbendlin]

See how you have nested "each"  ?  That's asking for trouble.  The Power Query engine can be confused and grab data from the wrong context. Use function notation instead.

[lbendlin]

Learn about scope - the Power Query equivalent of context.  You can use function notation instead of "each"  to clearly identify your context layers and address items in each.