Creating scout groups
To segment your scouts while they're completing a mission, just click "add group" at bottom left of the scout management page. Once you've created the groups you want to use, just click on a scout–or multiple scouts–to highlight them, then click "move to..." to place them in a group. (You can mark multiple scouts as "mission accomplished" or "closed" following this same procedure.)
To message only the scouts in a group, just filter by that group, select all and click on the message icon that shows up on the tables toolbar.