These inserts attach to their neighbors using 3x2mm magnets preventing them from rattling around. Easily extract components from the stored reel by pushing down on the components and moving your finger backwards.

The design was made using FreeCAD 0.19 pre and contains a spreadsheet where all parameters can be adjusted.

8mm and 12mm wide reels have their STL's uploaded since those were the ones I needed.
Magnets are glued in place after printing.