I am sorry to hear about the resizing issue with nested columns. This misbehavior is similar to a previously submitted bug in our public feedback portal and it has already been resolved.
I can confirm that the behavior that you want to achieve will be supported in the next release or internal build of Kendo UI. At this point, I can't give you an estimate for that, so please check for updates. Do not hesitate to contact us again, if you need further assistance.
Thank you for your patience and understanding.
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