"After setting up the Other Asset account for collections, when you are entering as Other Charge, do you link it in the Income Account"

You already have income from the Invoice.

This New Item is linked to the Other Asset account. That allows you to use it on the credit memo, to Close the AR balance (AR is a type of Revolving Asset by names) to a different Asset account (waiting for collection).

"and select " This item is used in assemblies or is a reimbursable charge?"

No; you don't need it to be Two Sided. It has One Account that it is linked to, and flows data to = Other Asset.