If you want to lock an actor to a special part of the crane (like the hook or something), the above method won’t work. Try one of the following:
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If you want it to be there from the start, drag it into the crane BP as a child of the (moving) component you want it to be attached to.
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If you want to be able to change it at runtime, you would need to implement some inputs first, also think about how you want to distinguish which actor you want to attach when you press a button (like an overlap event of the “hook” component and an actor in the world) and then use AttachToComponent for said actor and attach it to the hook.
The more clearly you specify what you’re trying to achieve, the easier it is for us to help you 
In general, most of the time you try to fake things and make them look real, instead of actually making them work in a realistic way.