Right clicking an assignment brings up the right-click menu with further options:

Brings up the quick editor. 

Enables split mode. Your mouse pointer will change to scissors and the assignment will show all possible cutting points.

To split the assignment into two, simply click at the desired cutting point. If the assignment to be cut has a note, the note will be retained on both assignments.

Enables you to duplicate the assignment across several people.

Allows you to transfer the assignment to a placeholder or another person.

See the Placeholders help doc for more information about using placeholders in your planning workflow.

Enables you to select all the assignments to the right (in the future) for a person and drag them across the timeline in bulk.

Enables you to select multiple assignments for multiple people and drag them across the timeline in bulk. 

Deletes the assignment and assignment notes.