This is a shortcut for accepting any selections or changes in a feature. The indicator pops up beside your cursor typically after you’ve made a selection. A simple right-click quickly accepts the command. But for all you fast mouse movers, don’t stray too far because this shortcut will disappear if your cursor is moved from your last selection.
There are many situations when this shortcut can be used so keep your eyes open. Some examples are extrudes and cuts after dragging the depth arrow or selecting an “Up to” end condition. Or quick features like Planes and Mirrors.
This is also very useful for features where you need to jump to the next selection box, such as the Full Round Fillet. Since you can make multiple selections in each box, it doesn’t automatically jump to the next. A simple right-click will allow you to move along quickly without the need of dragging your cursor back and forth to the PropertyManager.