How can I pop the last element from one array and append it to another?

adam_gataev - you have the right terminology.  Just use a Mapper as follows:

Here I'm just using two Array methods: concat() and pop() to complete your goal in one expression.  The Array.pop() removes the last element and returns that element.  The Array.concat() creates a new array with the new element added in.

Note that I'm also using the "pass-through" option on the Mapper settings.  This allows any other elements in the input doc to flow through to the target path without specifying them.

Hope this helps!