In the campaign, objective popup overlays are used to inform the player of a new objective. The respective Lua API calls is ShowObjectiveTextPopup and uses a localization path for the input text.
Note that the popup will pause the game in singleplayer.

In the campaign, objective popup overlays are used to inform the player of a new objective. The respective Lua API calls is
ShowObjectiveTextPopupand uses a localization path for the input text.Note that the popup will pause the game in singleplayer.