In the BPMN2 Modeler can be invoked context menu by right click on any process element. For tasks such context menu contains option Morph Activity. Behavior of Morph Activity option is not consistent with other options like Append Activity.
Append Activity - to see sub-options it is enough to move mouse over this option
Morph Activity - to see sub-options it is needed to click on this option
Behavior of Morph Activity is the same as for Append Activity