Yes, it's exactly that. If I want to set a different background color for the `mode-line-buffer-id` when the buffer is inactive, I can't do it with the faces options of the `mode-line` group.

On Sun, Jan 30, 2022 at 1:18 PM Lars Ingebrigtsen <larsi@gnus.org> wrote:
José Júnior <jjnilton@gmail.com> writes:

> Mode-line has face options for when it's active and inactive but
> `mode-line-buffer-id` just allows customization on the active form,
> please consider adding the option to allow customizing the face of the
> `mode-line-buffer-id` when the mode-line is inactive too.

I'm not quite sure I understand the request.  Do you want to add a new
face for the buffer identification part of the mode line when it's
inactive?

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