v1.94 has been released.
It adds the ability to adjust the number of color swatches per row in the Map Palette.
I don't think it's exactly perfect. Among other things, the UI for it is a bit clunky. But it does work so I figured it was better to post the update than make you wait for me to figure out how to UI it all nice and clean.
Give it a go when you get a chance and let me know what you think.
Some things to note, the example palette you gave has a few duplicated colors. Two of the grays IIRC. This throws off their appearance in the tool because the tool simple scans input files for UNIQUE colors. I went ahead and added a version of the palette with all unique colors to the set of sample palettes that are included with the tool. Long term, I'd like to make the tool smarter about handling duplicate colors when loading from a file that is obviously a set of palette swatches (the current behavior is more designed around extracting the palette from an arbitrary image), but again I didn't want to make you wait while I figured out how to make that happen. One work around would be to save the image in an indexed color format as the tool does support duplicate colors when importing from indexed files.
Thanks!