Prevent drag & drop on Django admin when user needs to filter first

[mbrochh]

Sometimes a model has FKs to several other models (let's say an Event has a FK to "Category" and "Type") and the positioning should not happen based on all objects of that model, but only based on a certain subset. For example, only all Events that are categorized as "China" and are of type "Art Fair" should then have a custom positioning.

It would be cool if we could prevent the drag & drop javascript form kicking in until the necessary list_filters have been selected.