1. Enable multiple MDI windows for file comparison.
2. Disable multiple MDI windows for folder comparison.
3. Open a folder comparison MDI. Open its files for comparison.
4. From the Windows File Manager, select two folders and drop them onto WinMerge.
5. Now the folder comparison MDI which was opened in step 3, gets replaced, but did not come to focus.
6. I guess those MDI windows with files which were opened in step 3 should be automatically closed, too.