I believe what you are looking for is constraint type. Please see the information below explaining how you can add one.
Setting Constraint Type
- Navigate to a work item Properties Card.
- Click and scroll down to the Schedule Settings section.
Figure 1: Schedule Settings
- Click the Constraint Type value field to activate the dialog.
Figure 2: Constraint Type Dialog
- Define the required constraint type.
The dialog closes.
The work item constraint type setting is set as defined.
The change appears in the Properties Card Schedule Settings section.