If an Effort has not yet been launched, it can be deleted to keep your Effort Calendar neat and streamlined.
Click on the unlaunched Effort so that the sidebar appears on the righthand side of the screen. Click on the three lines in the upper righthand corner of the sidebar and select Delete Effort.
Alternatively, hover over the unlaunched Effort and click on the trash can icon to delete.
If an Effort has been launched, it cannot be deleted. The only options available are Open Effort or Edit Effort.