Add them to an array in the desired order, have the slider step through the array and set visiblity.
I think there might be a bit of confusion here. @Gerard979_3D are you talking about Visibility only? Because when you say:
By moving the slider tick, actor A starts to disappear while actor B appears little by little.
It does sound like translucency, indeed - for which you would absolutely need materials.
If you want components / actors pop in / out of view instead, this could be done with just setting visibility and / or material.