[Bug/Ui][3A] There is no way to permanently Retire a Unitdesign

I designed some units. After redesigning the unit (by using the upgrade button) and changing some flavour text as well as the image, I retiered the first design. Obviously i would no longer use it.

However during the next game both designs reappeared and i had to again retire the first (bad) design. Therefore, a button to delete an design is obviously missing, as this function is not performed by the "retire" button.