We can create work item by using process flow only.So screen flows cannot be starter flow.

Hi PriyaG,

When you select the category as Screen flow on the Design tab of the Flow rule, you will see that on the Process Tab "Create a new Work object" check box is greyed out and does not allow you to create a new Work object and hence cannot be used as a starter flow.

Screen flows can operate only on Work Object created by the parent or the starter flow. It doesn't have any significance stand alone. If you think about it, screen flows should be thought of as a sub flow because it doesn't create multiple assignments as such, it is just a list of flow actions that has to be run by a single user.