Very slow close of a popup with a list view

A popup with a list view takes a very long time to close. The list view is destroyed one item at a time. This happens when the popup is closed with the close button in the popup header or the default Save and Cancel buttons. A microflow button that does a close page action closes the page immediately. I created ticket 205841 for this.
1 answers

This is the default behavior of the save button.

Whenever you use a dataview, with the default save button the platform will commit each editable object. It does that by identifying all editable objects (dataviews), and doing a commit per dataview.
This might be something the client should be able to batch.

You can easily optimize this yourself, if you replace the save button with a microflow. In that microflow you can retrieve all associated objects (by association) and then do a batch commit on the retrieved list.
This will give you a significant performance improvement.