I already answered to this query in duplicated support ticket created by you - #913629 . Please keep in mind that it is highly recommended that you keep related questions in one support thread or a forum post, so that we can easily keep track of your support history and provide better answers in a shorter time.
For convenience I also include the answer from the support ticket below:
You can for example use the "dateHeaderTemplate" option to insert the checkbox above the rendered date. For convenience I created small example which shows how to achieve this:
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