@Sk Mafar Ali Welcome to Microsoft Q & A Community Forum. Kindly note that it isn't possible to track user who modified the file. To track the file content changes, it's not possible to track changes using KQL, but you can track in portal. For more information, refer to this document.
Also, as the file content changes are stored in storage account, the link to specific files is available in Log analytics workspace with column name as "FileContentBlobLink"
As this is new feature request, I also would recommend you navigate here and share your feedback or suggestions directly with the responsible Azure feature team and clicking the vote button of your suggestion to raise visibility and priority on it.