Have you looked here?
https://docs.larian.game/Dialog_editorAlso watching Windemere's editor tutorials, might help you?
https://www.youtube.com/channel/UCPluKBMpyuCEnPbbknXL-nw?ab_channel=WindemereRPGThat being said, I'm not sure about how GM works, but it looks like you have to use story script to achieve that. Fortunately for you one of Windemere's tutorial covers how to have certain dialogs option open/close up as a consequence of other actions. Like someone being freed from a cage.
