Appending item to a list nested within another list

Hi Everyone,

thank you all for your answers!

I get it is not straightforward to append the element where I want in a simple way.
I would prefer not having to flag the entries of the list, but it is likely the approach I might adopt in the end, as @Mark_Smith suggested.

Still, I didn’t get why the arrayFilters I am using are not working.

In any case, I was thinking: would it be possible to exploit some reverse operator on “testHistory” so that we can match the first elements of the reversed list?

Thanks!
Francesco