Hello,
in VMware Cloud Director 10.6, there is new "switch" for changing the theme, either light or dark.
Does anybody know if this option is only for build-in themes?
According to official documentation Customizing the VMware Cloud Director Portals by Using the BrandingThemes API seems that you can assign only one custom theme for a tenant, so either light or dark without possibility of switching.
If you are asking how many themes can be applied to one tenant, the answer is One.