Cause

No variables were defined when assigning the value.

Solution

1. Double-click the placeholder object. In the Placeholder object dialog, bring the Values tab to the front.
2. Define at least one variable here. To this purpose select the popup menu New variable.
3. In the Name new variable dialog enter a name and confirm the entry by clicking [OK].
   
   The variable is added as a new row under the column heading Variable.
4. Select the New value set popup menu item.
   
   An empty column is added to the table.
5. Enter a designation in the top cell of the column for the value set. Enter a value for the variable in the second row.
6. Switch to the Assignment tab.
7. In the column Variable, highlight the cell with the object property you want.
8. Select the Select variable popup menu item.
9. Assign the new variable to the object property you want in the next dialog.
10. If required, start a new check run.