  We discuss the growing interest to measure associated-quarkonium production
in a number of channels at the LHC. Whereas back-to-back production of
quarkonium + isolated photon provides a unique way to extract gluon TMDs,
observables such as quarkonium + W/Z can be of great help to better understand
the quarkonium production mechanism as well as to shed light on double-parton
scatterings. Along these lines, we also argue that quarkonium-pair production
is a potentially rich source of information which only has started to be
harvested. Finally, we discuss the relevance of studying the production of
quarkonium + heavy-quark, as e.g. J/psi + charm and Upsilon + non-prompt J/psi.

High Energy Physics - Phenomenology;High Energy Physics - Experiment;Nuclear Experiment;Nuclear Theory