This toothbrush holder is parametric and will add holes for however long you want it to be with whatever spacing between holes you want. It only adds holes lengthwise and will always be an odd number of holes, with one in the center. You can also change the width, height, size of holes, and curvature of the corners.

All this is easily changed in OpenSCAD, a free, lightweight code-based 3D modeling software.

Enjoy!