Action Sample Project demonstrates registering actions process in various configurations. Each action is an extension of the AnAction abstract class and brings the possibility of extending IDE with an event performed with the user interaction - i.e., clicking the button, using the keyboard or mouse shortcuts.

Plugin registers the PopupDialogAction action, which provides a popup dialog as a feedback, in three different ways:

by assigning the keyboard (Ctrl/Cmd+Alt+A, C) and mouse shortcuts (Ctrl/Cmd + Mouse Button 3 + Double Click),
by adding action item to the ToolsMenu group, available in Tools menu,
by adding action item to the EditorPopupMenu group, available in Editor's context menu.

Actions

ID	Implementation	Extension Point Class
`org.intellij.sdk.action.PopupDialogAction`	PopupDialogAction	AnAction
`org.intellij.sdk.action.GroupPopDialogAction`	PopupDialogAction	AnAction
`org.intellij.sdk.action.CustomGroupedAction`	PopupDialogAction	AnAction
`org.intellij.sdk.action.CustomDefaultActionGroup`	CustomDefaultActionGroup	ActionGroup
`org.intellij.sdk.action.DynamicActionGroup`	DynamicActionGroup	ActionGroup

Reference: Action System in IntelliJ SDK Docs