I'm not using the column testChoice and when I use the ColumnName Value it creates a new "Apply To".
this is what happens when I select the ColumnName Value: it throws in a a new Apply To 3 and changes the select output to current item and then the Append to string is inserted there:

this is different than your example with this happening, any way to actually use the "Apply to" with Multiple Selection Choice Dropdowns?
When I select the column Name with out the "Value" just this :
ColumnName from the dynamic selections and use it in the flow I get
The execution of template action 'Apply_to_each_2' failed: the result of the evaluation of 'foreach' expression '@items('Apply_to_each')?['Column Name'] ' is of type 'Null'. The result must be a valid array.
when I do the other suggestion:

I get data entered but it is incorrect:
12312341231234132 and I get everything in the columns as
the last item 132 is what I entered, it picks up all the other entries. I only want the new data.
sometimes it grabs all the prior data and places it in 1 column. starting with {"@odata.etag"........}

I just need the new item entered, not the entire list.