I wanted an expandable shelf, but didn't really see much that I liked.
It prints in 4 parts. You need 4 M3x8 screws, 4 M3 4x5 heat set inserts and two wood screws or drywall screws to hang it in the wall.
I highly suggest a brim, or mouse-ears if you use Orca. 3 walls and 20% infill should make it super sturdy.
It has a hanger rod underneath, to add to the shelf. Hang keys, hang your phone, etc. I'll be adding expansions to it soon. Feel free to post remixes for it yourself.
The author marked this model as their own original creation.