To edit an existing Widget go to the Manage Widget page & select the Widget you want to edit & select the action, Edit:
The Widget form is open & you can edit any field but don't forget to save your changes!
Of course if you want to create a new Widget and leverage some of the details you have already set up (i.e. links, UTMs, messaging) you can also duplicate a Widget rather than starting from scratch. Select the action, Duplicate:
Can't find your Widget, read this article.