Syndicate certainly lets you factor out some kinds of repeated behavioral patterns: I discussed in my dissertation (chapter 9 [1]) examples around cancellation, around state-machines, around observers, and around demand-matching.
Besides these examples, the general facets-plus-conversational-context idea lets you factor out composable behavioral traits. Which word reminds me of the Traits of Schärli/Nierstrasz/Ducasse [2]: those Traits have proven benefits for improving reuse and reducing redundancy and bugs in Smalltalk systems. So perhaps in general what we're looking for are new perspectives on old problems - new ways of isolating and composing ideas.
Strictly on the example of dragging objects, I actually have a little demo GUI that factors out object draggability into a composable facet of behavior that can be "mixed in" to an actor representing a graphical object. See [3] and, for detail, [4].