The Transition activity cannot be dragged from the Activities Panel, like a conventional activity. It is generated when you link a State to another State or to a Final State, within a State Machine container. (Refer figure 1.2)

Technical Reference

States can be linked to multiple Transitions, each describing a possible way to pass from a State to another.

Activity: This activity helps you input conditions under which the automation project can pass from one State to another

Figure 1.2

T1 - represents the transition from a state to another within the container.