Format mask in silhoutte

There is a format mask option at the top right of the silhouette.
This option is always disabled. How to enable it?

Only certain Session types have masks associated with them. The Sessions are specified in the formats.xml file in the Silhouette/resources folder of your installation. Some of these Sessions have masks and some don’t. There is also a masks.xml file located in the same location which defines the mask types.

You can add your own custom masks to the masks.xml file. The rectangle values are multiplied by the image width/height to figure out where the mask should be placed. For example, Safe Action is a 90% rectangle, so the border is .1, .1, .9, .9 (i.e. 10%, 10%, 90% 90%) of the image size.

You associate certain masks with certain formats by adding a “Mask” entry to the formats in formats.xml. You can add any number of masks to each format. These masks will be available in the mask selector in the Viewer, depending on the session format.

Note: You can’t associate masks with “custom” session formats. Instead, you should add a new format to your formats.xml file if you have an odd format you want to use with masks.