Created attachment 131886 [details] Screenshots of preference and undesired behavior. The remote files dialog is forced to open in a new window with two tabs when the macOS "Prefer tabs when opening documents:" preference is set to "Always" in System Preferences > Dock on Sierra 10.12.3. See attached screenshots.
Ugh, that looks wrong indeed. Thanks for your report. → NEW
I like the updated summary... the tabs are indeed "useless". I'm happy to help! LibreOffice is a fantastic piece of software and I hope it continues to grow in usage. Please let me know if I can be of any further assistance.
*** This bug has been marked as a duplicate of bug 114985 ***