I can see in the documentation that following types are allowed for custom property of an extension: integer, number, boolean, string. Is there any way I can satisfy following need? I'd like to give users possibility to add multiply properties of the same type to the chart. For instance that could be a color. So for instance you could have a section "Color palette" where user could add any number of custom colors they want to define - similar to dynamic number of dimensions or measures you can add / remove.