You can create a Custom Event.
rightclick and type “custom event” and the Context List will guide you to it.
This event can be called withing the same BP or via a reference from another BP Class.
That way, you can create your own while loops by simple call the event, inside the event again. But make sure to add a branch to break it. the difference to a Node While Loop (that runs within 1 Frame) is, that you can add a Delay Node to make the Loop wait for N.xxx Seconds and let other actions happen in between that delay.
PS. : Delays can not be used in Functions, just in a normal BP Graph.