It's unclear what activities the cancel button starts when one opens a file (not a project) with a double click (not via File>Open file).
I've tried to open a file in a new tab of current window and always seen this window ->
I thought that "Cancel" means do not open the file at all, so I was clicking New window or This window. Once I occasionally clicked Cancel, and wow!, the file was opened in a new tab! I think there should be another name for this button, something like "Open in a new tab"
Also seems that "Remember, don't ask again" checkbox doesn't work. I've checked it and clicked "Cancel", but when I opened the same file one more time, I saw this window again and again.