Although there may be a formal definition somewhere in a dictionary that draws a subtle distinction between the two terms, I would say that for all practical purposes they are interchangeable.
I met several user interface designers, developers, etc. who simply change these terms left and right. “List Management,” “List Widget,” and even sometimes “Gadget List.”
I even saw how the GUI tools there define a "widget" as a "UI control" and a "UI control" as a "widget", which gives us a good recursive definition.
If you look at something like Qt, "every UI control is inherited from QWidget" (everything from buttons to the most complex controls).
Given that many people use these terms interchangeably, I would say that it is perfectly acceptable to do the same, even in a technical document. This does not mean that the status quo determines the correctness, but I do not know any authority that defines this outside the status quo. Perhaps you could do better than most by simply sticking to one of these two terms in sequence.