Warning: if this feature is implemented, many academics could position MarginNote more centrally within their workflow. And as academics, whom are in the business of teaching and modelling knowledge work, recommendations and adoptions would grow in quantity to students. That means more students using MarginNote!
That’s my way of +1’ing the OP’s feature request.
Before expressing my thoughts, I do not think MarginNote ought to invest heavily into emulating features of citation management software, at least not as of the current release. Instead, there should be a lightweight method of keeping annotations within context and citable without much developer time investment nor a hyper-focus on citation management. I thus second the above implementation by @Spoon with a slight adjustment, and offer a more robust alternative.
The ideal end goal would be, as I see it, to have a full-text citation rendered at the top of the exported annotations file, and in-line citations formatted next to individual annotations. However, given MarginNote would have to support a range of citation styles, a smaller implementation is more plausible.
Suggestion #1:
Scaling down the end goal, then, add the ability to automatically append user-defined text to excerpted annotations. What I’m thinking is to add two fields in the document’s info pane to predefine text to append to annotations. The first field would contain a full-text reference, and would serve as user reference and for export; the second field would contain an in-text citation, and would serve as the text appended to the bottom of the annotations. To accompany, include the preference: “Append and show custom text” in the preference menu in addition to, “Include text upon export” in the export menu.
Users could then copy and paste a full-text reference and in-line citation style of their choosing from their citation manager. The in-line citations would include page numbers with a link back to the annotation, as pictured in Spoon’s above example. This would allow document titles to remain separate from appended text, while no citations style would have to be supported. Student life would be oh so easier.
Suggestion #2:
Alternatively, consider the idea of Excerpt Templates. With an ability to add information into separate fields of the document info, users could define their own fields like ‘Author’ and ‘Year’. A template manager could then allow you to format excerpted annotations. For an example:
”$SelectedText”, ($Author et al., $Year, $PageNumber&NoteURL=1)
…would translate to:
”The second model Chomsky calls a model of linguistic performance, because it models how speakers actually use their linguistic competence.” (Akmajian et al., 2010, p.6)
In this hypothetical example, $, & and = are used as special syntax. In between are attributes, with SelectedText, PageNumber and NoteURL as native attributes, and Author and Year as possible custom, user-generated attributes, and 1, a boolean on/off value. Of course, this particular example is for illustration purposes, but a fully fleshed out template manager could address the citation problem while catering to every user and use case, not just academics and students.
With the core idea conveyed, I’ll leave Excerpt Templates as a potential solution to a central need of academics and students, with the goal of starting a conversation here on the forums.