How it works
This function will delete all the tickmarks that have been made within the sheet you are in, along with the legend.
Note: This function is only available for Image tickmark types.
How to delete all tickmarks:

Step 1
In the more drop-down in the Ticking and Bashing group, click on Delete All Tickmarks.
A new pop-up window will be displayed.

Step 2
Confirm that you would like to delete all tickmarks by clicking Ok.
On completion, all tickmarks in the current sheet will be deleted along with the legend.