You could make a button that looks like a link to close all and then open (
Action navigate } a named tiddler, but I think you want this to occur for all links?
Of course such a button could close one, and open another leaving the rest of the story intact but how do your define "The
existing one?".
I have a way to "focus" on the last opened or a selected tiddler, if that is required.
Tones