TreeDataGrid theme?

Yes, TreeDataGrid is something we plan to support. Since the project is currently listed as "early beta", though, we were hesitant to add support until it reached maturity.  The Avalonia development team may still be adjusting some of its control themes so we probably will hold off a little longer before working on it.

any plans for this? TreeDataGrid seems to be stable ...

Hello,

After checking with the Avalonia team, it sounds like that TreeDataGrid control is still in a tentative state and will possibly be moving to their Accelerate offering in the future.  We will probably hold off for now.  That being said, you can use any of our brush resources to make a custom control theme for the current TreeDataControl control that matches the look of our other controls.  Since you are an Actipro Avalonia Pro customer, you can download our control themes and can use those as a reference for which brushes to use where.