in the Data Manager we can click Import, we can click the dropdown arrow next to the Import button, where the alternative "Import and Duplicate" is given.

This is dangerous because there are no overwrite warnings anywhere, so any user who chooses the wrong option can easily lose data.

If we change the default "Import" so that it always duplicates, and then offer users the alternative option of overwriting instead, then anyone who makes a mistake here won't lose data. They can easily delete the extra data instead.