Modern henotheism/monotheism includes Ayyavazhi and then Bahá'í, before Theosophy and the religious figure/prophet Dr. Dahesh after Theosophy, and the still alive person who has been called Maitreya (http://www.maitreya.org,) who people say has fulfilled some Bahá'í prophecies, but some Dahesh followers think is a 'false prophet' for reportedly calling himself Christ. I do not know if Dahesh fulfilled Bahá'í prophecies, but what do you think of these people/groups?

I have done some Bahá'í reading and think it is a great, if rather exoteric (though it references Theosophy) philosophy. I do not know much about the rest. Of course another great modern henotheist after Theosophy was Paramahansa Yogananda. He may not have founded or reformed a religion (or have miracles ascribed to him like Dahesh,) but compared to some of them he may have had more intellection--or should I say, intuition and inspiration (since the former ones are increased by the latter ;) having utilized this higher consciousness of the spiritual triad and ideal forms rather than the ghostly/emotional/instinctual body/form/process that is the base of exoteric religious blind faith.

Also, another recent (1974?) henotheist/monotheist religious event is the Jain sects created a common text: Saman Suttam. Jain Dharma varies from Sanātana, but seems about as deep and worth studying.