A new user (do a test with a neighbour ) should be able to clearly understand 

1/ in 5 sec the input and the output of the tool (the main functionality)

2/ on every step the next actions available (the path)

Not easy the first time to understand to drag and drop from the left part to the middle. In the middle, what is a cluster ? why the drag and drop on the cluster line do nothing ? some files are moving to the right ? but not all of them ? Need to take an album on the right to drag and drop as a cluster (and the album name is now the folder name)

Proposition: 

• always from the left to the rigth
• one visual for the files, one for the albums
• left : file to scan (ex: https://tickets.metabrainz.org/browse/PICARD-1836)
• Middle : split on few sections with a stack of status from the top the down 
  • file : number of selected files from the left
    • file: to scan
    • file: scanned
    • file: cluster 
  • albums:
    • completed
    • to check
    • .. 
• rigth : a view on one or many sections from the middle part (need selection on the stack items)