I've been using nodered for years now. From time to time I get lost while changing the existing flows and want to start from scratch by importing it again from the backup-file. My backups contain all existing flows of nodered (32 btw.). After selecting the file nodered nodered tells me that some of the nodes I'mimporting already exist in my workspace. so Now I have to deselct 31 flows because I want to import only one flows to restore.
So my suggestion for further releases would be to create a checkbox to select / deselect all flows to simplify that.