I’d like to have a slider in my options menu, that will allow me to manipulate audio effects volume / music volume / dialogues volume. How do I do it? Thanks!
You can use a slider widget (https://docs.unrealengine.com/latest/INT/Engine/UMG/UserGuide/WidgetTypeReference/#commonwidgets) in your UMG Menu Options for every volume you want manage.
Click on a slider, choose OnValueChanged Event (https://docs.unrealengine.com/latest/INT/Engine/UMG/UserGuide/Events/index.html) and create something like that: