Go to Sequences.
Right-click (or long-press on a touch screen) on the sequence you want to delete and select “Delete” from the drop-down menu.
You will be asked to confirm whether you want to delete this sequence. A sequence cannot be recovered after deleted. Make sure you have backup just in case you want it back later.
You can also select multiple sequences you want to delete using the on the toolbar, and select “Delete” from the toolbar.