Problem displaying tasks for both parent and child records in same table

If I am understanding you correctly, your table is on a parent record detail page. In that case, there is only one parentRecordId in context so when you add a condition of WhatId=ParentRecordID it knows that ParentRecordID must be the only ParentRecordID in context (row 0). Adding a condition of WhatId=ChildRecordID may confuse it as it doesn’t know which ChildRecordID is in context since there could be many for each parent. I think you would need to change your second condition to look through the child record to the ParentRecordID. So instead of WhatID=ParentRecordId, you would have to set the ParentRecordID of the WhatID equal to ParentRecordID. I’m not sure if tasks let you look into the fields of the WhatId to find the ParentRecordID. If not, then you’ve got some issues. You may have to do two separate tables. The first table would be your original parent task table. The second table would be based not on the tasks object, but on the child record object. This would list all the child records of the parent. You would then add a drawer to that table to display the tasks of each child record. Someone else may have a better solution and I have limited experience with conditions on the task object, so I may be off in my thinking. Good luck.