I have a SharePoint task list that has exceeded 5000 items. I have a created a custom list that has just about all the columns of the task list. My intention is to copy a large backlog of the items in the task list to the custom list as a sort of archive. My preferred option for achieving this is using Microsoft flow. However, one stumbling block I am facing is that the flow fails when the AssignedTo in the task list is a SharePoint group. Apparently, I can't populate "AssignedTo Claims" with the display name of the SharePoint group. Has anybody faced similar issues? Will deeply appreciate a solution or suggestion. Thanks.
In addition, I can't use retention policies because it is absolutely essential that I preserve fields such as "Created By", "Modified By", "Created Time", "Modified Time" and if possible attachments. I have created equivalents of these fields in the custom list.