In this set of other concepts, three sketches will be presented.
The first sketch consists of a perforated board that has a removable shelf that can be hung from it. The shelf is easily hung on the board and it can be located wherever the user wants. Also, several boards can be put together to form a bigger one. An alternative to the shelf can be a bag that can be hung on the board.
The second sketch is a traditional shelf, but with the peculiarity that the shoes can be stored in a vertical position so that they take up little space. The front part of the shelf can be removed easily to grant easier access for cleaning.
Finally, the third sketch consists of a closet that is either vertical or horizontal, and which has doors that slide instead of opening forward to ease its access in places where there is not much space. The shelves are inclined so that the shoes can be reached easily and the closet is not as large.

ODEI | DESIGN TEAM 20
It is so good to see different options and there are feedbacks for each of them below.
Sketch 1: Actually playing with the shelf and giving freedom to user to locate it, might create confusion also we had some difficulties to understand how shelf attacthed to the board.
Sketch 2: This is also another different approach but we are not sure about storing shoes vertically because it can damage the structure of shoes.
Sketch 3: For the last idea not the horizontal one but the vertical slider system might be efficent considering as the limited space. Only bending down created a question mark from our side.
Thanks for your effort!