If Thomas says it can’t be done for now maybe some lateral thinking solution can achieve something similar. I am new to Skatter so by no means an expert, but perhaps you can get around the problem by a disciplined naming convention? I use such a convention to manage Sketchup’s layers. My Sketchup models are large by Sketchup standards (600Mb plus) and I have to use layers and scenes to their maximum to manage loading and rendering. I hate having to scroll aimlessly through hundreds of random layers looking for what I want so I prefix each layer with a category name, for example,
Maybe if you used a similar prefix name convention you could organise your Skatter Library the same way - it depends if the Skatter Library Dialogue uses an index to reference its internal database? If it works you would not have folders and sub-folders but you would have logical organisation. I am trying to build a Skatter Library now so I will try this.