When you attach a waypoint to an object, doubleclicking it won't allow you to select the type.
There are several things it would be desirable to do here.
Get in is somewhat a default.
Follow may be currently not be possible.
Load cargo would be appropriate for sling loading.
Currently you just have to set the waypoint and hope it's the right type. In many instances where I want to load cargo I instead end up with "get in".