The problem is quite deep into the existing layout logic of the ColumnGrops Arange logic and fixing it in our existing implementation is not possible. The fix consist of redesigning the entire rendering engine for the merged headers which is why it takes longer time to fix. The plan is to introduce a new render mode for the Headers much like the GroupRenderMode property. The idea is to keep both render modes so no breaking changes are introduced.
Due to the nature of the work required and the time it would take to complete it, we cannot commit to a certain time frame at which the work will be done, however we will do our best to include it in our main planning for our Q2 release.
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