Wow!
A revolutionary feature in TW 5.4.0 is two new attributes for linkwidget startactions and endactions on drag-drop links. (Same for list-tagged-draggable, list-links-draggable)
While there are few examples in official documentation, but I like to see more applied examples from developer and experienced users.
The link-widget documentation contains an example how to use it. See: Action Variables section.
It is basically used in the same way as “button actions”. The difference is, that the actions are “triggered” on “drag-start” or “drag-end”.
The list-links-draggable and the list-tags-draggable macros have “internal” drag-start and drag-end actions.
The new ones are additional user actions, that can be used on demand. Where demand varies on the use-case.
Help is very welcome here. If you stumbled upon a missing “drag-??” feature in the past, please let us know about your use-case.
I just found out, that a link to the the modifier variable may also be useful.