How to add action programmatically into main toolbar

never mind, I figured it out, I was so close the whole time, unfortunately I was using constant ActionPlaces.MAIN_TOOLBAR, which is "MainToolbar" :|


DefaultActionGroup mainToolBar = (DefaultActionGroup) ActionManager.getInstance().getAction("MainToolBar");
mainToolBar.addAction(...)

The constants in ActionPlaces are not action group IDs. The constant for the group ID that you need is IdeActions.GROUP_MAIN_TOOLBAR.