Create a child incident links two or more incidents between each other in a "parent-child" model. To create a child ticket, please complete a following steps:
Start creating a new incident in a way as it was described here;
Fill in the form, then scroll down the page and press the Related Records tab;
Unlock Slave Incidents. For this, press a lock icon.
Press a magnifier icon to select incident that will be parent for this one. You can select over one incident, in this case all of them will be parent for it.