Where is the custom color tab?

[Moes81]

Hi!
In previous versions of the plugin, there was a "custom" tab, where I was able to select my own colors for the color scheme. That tabs is no longer available. Instead, we can set somewhat general colors "primary", "secondary", .... "neutral", "neutral variant". But, the MTB then creates a theme from those color, but differently than expected. The primary, secondary, tertiary colors are nowhere used. Furthermore, if you already have a color scheme, then you cannot enter those colors anywhere.
How is this intended to work now?
How can I assign, e.g. a "primary" color, that is actually used as "primary"?
People seem to have a hard time to figure this out:
https://www.reddit.com/r/MaterialDesign/comments/15v1lsa/how_do_i_set_up_the_color_theme_for_material/
https://www.figma.com/community/file/1035203688168086460 (see comments section)
https://stackoverflow.com/questions/70314302/how-to-create-own-brand-color-style-using-material3