Configurable line colour between header and story

[KathrynHailes]

It would be great if the colour of the line between the header and the story could be configured as part of the theme. As an example, refer to the thin light blue line in the screen shot below.  Many organisations are required to adhere to strict corporate brand guidelines and not being able to configure this causes challenges.

Thanks for your consideration.

Original post here Re: Blue line under header in Storymap Theme - Esri Community