One more level for theme edditing

Hello,

I have very large mindmaps and it would be very helpful if I could edit theme in 6 levels, not only 5. At the moment in the "Design", if I click "Edit theme" and then "select style group level", I am limited by 5 levels. For the use of big mindmaps I would need at least one more level. In that way I could control its style (colour for example) and make mindmaps more clear.

Thanks for help and best wishes!
Martin