Based on @DROO's "The brand-new 2×2 three-way corner bracketThe three-pronged angle bracket of "..."

The holes are designed to be offset to avoid collisions between components. At the same time, the geometry is optimized to reduce the amount of consumables used and shorten the printing time.

The wall thickness of the exported model is 2.4 mm, which has already met my needs. During printing, a wall thickness of 3 layers is used.

The attached Autodesk Fusion .f3d file is a parametric model that can be flexibly adjusted in terms of size and wall thickness.