Currently, in ThemeBuilder there is a template that allows you to style the icon of a header cell that is filterable.

However, we need to be able to style the icon in a header cell that triggers the ColumnMenu (the more icon)

https://demos.telerik.com/aspnet-core/grid/column-menu 

https://www.telerik.com/kendo-react-ui/components/grid/interactivity/column-menu/ 

requested through t.1655985