It is possible to change the priority used for the selectors or even disable some of them by changing the setting Unassigned Items > Options > Order in Diagrams Options.

In the above example the search for a symbol starts according to the selector Settings. If this fails the search will continue according to the selector Specification. In this example the selector Manual selection will not be used.

When the right symbol is determined the Message Log displays a message explaining which selector was used during the operation.