Previously, if you were to bind a key or button to the "Use Selected Action" command, you were able to use it for other purposes when the action menu was not open. For example, how it is default in the Arma 2 control preset, having Primary Mouse button bound to both "Use Selected Action" and "Fire". This would allow to you to fire any weapon normally as long as your action menu was not open with an option. However, in the few most recent dev builds, the primary mouse button will no longer fire any weapon, even with the action menu hidden or it not having any options. If you have options in your action menu, it will then function as the "Use default action" bind did previously, and activate the most relevant one.