[Bug/Feature] "add to custom colors" behavior

[louisgag]

I'm using 0.19

When I change the colors of an object through the pop-up dialog there is an "add to custom colors" button.
It works, but if the color I want to add to the custom colors is that of the object itself (so that I did not manually select it through the color picker, for example) it will always end up in the first position.
If I try to change which custom color slot gets used it changes the color to what is in that slot (usually white).

I tried doing some shift-click, ctrl-click, etc but did not find how to avoid this.

Sounds like a bug or missing feature or just that I am missing something?