Selecting the Target Dependency means selecting which file you want to update from which existing Dashboard.
To configure the Target Dependency, click the “…” button :
Dashboard or Widget
You can select a published Dashboard or Widget by clicking at the top of the Select Target Dependency window :
Browse Categories and Dashboards in the left pane :
After clicking on a Dashboard on the left pane, the right pane lists all its depedencies :
Click OK to validate :