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This behavior is controlled in list settings-> Advanced Settings-> Quick property editing: If you choose yes, we can edit directly without clicking on the "Edit all" link


1

There is no need to add ListItem.Update() when use reset listItem permission. Official document about ListItem.Update() for your reference: https://docs.microsoft.com/en-us/previous-versions/office/sharepoint-server/ee536748(v=office.15)


1

There is no OOB way to remove "Return to classic SharePoint" link. You may try to use third party tool as described below or vote this User Voice: https://support.shortpoint.com/support/solutions/articles/1000291926-hide-return-to-classic-sharepoint-link-in-team-sites#:~:text=If%20you%20do%20not%20want,Theme%20Builder%20to%20hide%20it. In addition, ...


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