I used this software some time ago to edit a couple MIDI files with mouse and (computer) keyboard, mainly for altering melody tracks, fixing some wrong chords and adding drums. I found this tool pretty intuitive to use and liked it a lot.
I had previously tried Sekaiju and another tool whose name I forgot, but I felt like they were aimed at more experienced users and assumed a higher level of knowledge about MIDI terms and concepts (of which I know very little), so much of the interface went over my head. MIDI Editor was good enough for my simpler use case.