Chords on a chromatic dulcimer are really easier than you might think. The diatonic chord shapes usually work. I like the L shaped chord, like the 1,1,3 E-minor. The third is on the melody string so that controls the minor-major shift. Move from 1,1,3 to 1,1,3.5 and you have E-major. Move this whole chord down (toward the nut) one fret and you have E flat major. Move it up and you have an F chord. When you run out of frets at the nut then the pattern has to change. Then it's best to think about what notes are in the chord. A B flat chord has B flat, D, and F. B flat is real easy to find on the A string at the 1/2 fret. D is an open D string. F is the 1-1/2 fret on a D string (three half steps up from D). I have never seen a chromatic chord chart but I don't need one.
Dulcimer players often ask me "why". Guitar players ask "why not".