A process can involve Events as well as Tasks. Events can have sub-types that you can use in a filter, or dependency, to determine whether a Step is started or not.
To add a sub-type to the Event Page Layout:
To add the Process Details custom button to Process Object Page Layout(s):
- In Setup, use Quick Find and type Event Page Layouts.
- Select Page Layouts.
- Select Edit next to the Page Layout you want to modify.
- Drag and drop the Sub Type field onto the page layout to the desired location.
- Select Save or Quick Save and repeat for any other page layouts that should contain the field.