No optical module for Canon 400mm f5.6 with 1.4x teleconverter (Mac)

Why isn’t there an optical module for the EF 400mm F5.6 lens with the Canon 1.4x II teleconverter? I tried to suggest this via the link in PhotoLab but don’t see any way to describe the need for the teleconverter.

It is a little frustrating to every other major Canon lens has an optical module with multiple 1.4x teleconverters when there is nothing for the 400mm. I assume this lens is really popular so I am quite surprised that there is no matching module.