I had to teach myself how to tag 3rd party content in the NKS format because I couldn't find anything about it online. I made a video documenting the process and I find myself sharing it from time to time in Facebook Maschine groups and on Reddit, because of others running into the same issue. One of the best things is that when your sounds are properly tagged, you're not limited to 2 folders on Maschine+. It'll read the tags over the folders! NI should really do an official video tutorial on this!
Here is a link to the video.