Greetings from Syncfusion Support.
Query: but it’s not working properly for collapsable column.The dots are not visible.
We have validated the defect you have initiated with us. Thank you for the taking the time to report the issue and helping us improve our product. At Syncfusion we are committed to fixing all the validated defect (subject to technological feasibility and Product Development Life Cycle) and including its fix in our subsequent release. So fix for the issue will be included in our upcoming patch release which is expected to be rolled out in the first week of August 2019.
You can track the current status of your request, review the resolution timeline and contact us for any further inquiries through this link.
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Until then we suggest you to use the below solution as work around,