I'd like to have the merge columns mode, for example like TrueDBGrid (desing time)

It's fantastic, and there is the vertical alignment

I've tried all yours codes to emulate it but it's too slow if radgridview has a lot of rows.

Thanks

Add Telerik Visual Studio VB template for NetCore

The SplitPanels should expose the Modifiers property so that it can be set to Public or Protected. This way it will be possible to work with the panels in forms that are visually inherited in the VS designer.

Add support in HTML like text formatting for subscript and superscript text.