Although I had a folder-question and nobody replied yet, I continued without help, trying to find out what works best for using my own 'sounds'. Although my thumb-drive wasn't showing any folders (it simply showed all sounds in alphabetical order), my SD-card was a better way to organise my sounds (User Content).
Connecting the Maschine+ in storage mode allowed me to make a folder structure. Some folders didn't show up. The content (AIF) in these folders I dropped in Adobe Media Encoder, exporting all sounds as new AIF's. I deleted the old files, and voila, after a 'rescan' in Maschine all my sounds (and invisible folders) are now available in Maschine+.
I read so many negative comments about Maschine+, that I felt the need to write something positive . I've been working with Maschine+ now for 7 days, allowing me to dive deep into all possibilities. I think it's amazing! All my own sounds pre-listen without hick-ups, Maschine is running smooth. I also connected my Novation Bass Station 2, receiving midi from Maschine and sending it's audio back into Maschine. It all works flawless, I'm really impressed!
It's amazing to have all these options available to you without the use of a computer. I'm considering buying a powerbank, simply because I would like to take this device everywhere! The idea of making music without a computer screen is something I always wanted. I changed my setup so many times, buying and selling gear, simply to find out that it's too complicated for me, spending more time on technical problems than creating music. When I wanted to continue a project I worked on the previous day, I first needed to 'activate' all other gear and select all setting on each device. This is so annoying if you're used to produce 'in the box'.
Maschine+ has made it possible for me to leave the computer screen behind and be unlimited creative wherever I want. When I load a project/song it's exactly how I left it, no need to pick presets on other devices or route audio signals through a mixer in order to hear everything.
So, yes, I'm very happy with Maschine+ !