Welcome Rudy! You will find many editing functions in the Index actions dialog under the menu Extras. When you open the dialog for the first time the list is empty.
A click on the [default] button fills the list with the most important functions, click on [ok] to save them.
The function invert names hides behind swap name, and makes Prename Name -> Name, Prename
In this dialog you can individually create further functions or adapt existing ones, they will remain in the list as soon as you confirm with [ok], even if you close idx.
You can access these functions via the index list. In the list, select the one or more entry lines with names you want to invert. Right mouse click opens a context menu with the list of index actions, which you only have to select. You can also activate the function via the short cuts indicated in the index actions list or set up your usual ones via the index action dialog.