While an interesting perspective (mention of the "medical purpose", "intention", "abuse") I don't see how these concepts could be well articulated with the MDR and more specifically with ISO 14971.
I think there are different approaches that can be taken. The following is what I would recommend as a first pass, for medical devices (per 14971)
"Off-Label Use" implies (to me) that the device is still being used as designed, but possibly as a treatment or therapy that is not supported by clinical studies, user validation, or otherwise cannot be
guaranteed as "safe" (in the 14971 sense) The product labeling/IFU should be derived from the greater design effort (including risk management) so I think concerns around understanding "off-label" use are pretty well understood.
"Misuse" falls more into the general category of
usability and should be considered as part of those efforts. Much like any analysis of failure modes, it is impossible to predict all of the potential misuses of a medical device, but a robust usability analysis will likely consider misuses in the areas of rule-based error modes, knowledge-based error modes, inattention, etc. My recommendation is to support those sorts of analysis in a document like a Use Failure Modes Effects and Analysis as a subordinate document for a Hazard Analysis... which ought to be fully compliant with 14971.