I am trying to create a custom theme with the "strong" background type.
However There is no customize button on custom theme and I do not see any json schema property for it.
Does anyone know if this is possible?
View best response
If anyone is interested, there is a new web property in the latest version of csom
So setting this via code allows a custom theme to be used with a strong background
e.g. context.Web.HeaderEmphasis = SPVariantThemeType.Strong;