1.) Upload the app and all corresponding triggers through the AppStore UI. For example I entered "DOOR,LIGHT,OVEN". The list will be shown in your BangleJs in the corresponding order so enter more important triggers first.
2.) Create an "automation" in the HomeAssistant WebUI for each trigger that you created on your BangleJs in order to tell HomeAssistant what you want to control. A sample configuration is shown in the image below -- I use this trigger to open the door:
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3.) Don't forget to select the action that should be executed at the bottom of each automation.
While playing and testing a bit I found that it is very important that you allow the android HomeAssistant app, as well as BangleJs Gadgetbridge app to (1) run in background and (2), disable energy optimizations for both apps.
Otherwise, Android could stop one of both apps and the trigger will never be sent to HomeAssistant...