In tabbed mode, when pressing alt key, it still activates top menubar instead of the tabs, which is a standard behavior in Windows. Accessing tabs using keyboard is important for accessibility and productivity. It makes the shortcut keys and interface discoverable by keyboard. LibreOffice is better than MS Office, thanks for the hard work! Hope this feedback helps.
LibreOffice does not implement the Windows Ribbon API to create its MUFFIN Notebookbar (NB) "Tabbed" UI. Accessibility and keyboard navigation is already well addressed with consistent keyboard controls. That is keyboard movement onto the NB's UI elements is via an normalized <F6> focus event onto the NB, the active "Tab" will highlight. While using <Ctrl>+<Tab> or <Ctrl>+<Shift>+<Tab> (or the cursor keys) keyboard actions to advance between NB tabs. Once focused into a NB assemblage of controls, keyboard movement is only by <Tab> or <Shift>+<Tab> to move between controls. Use <F6>/<Shift>+<F6> will advance focus between UI elements. And when Main menu is exposed (it is hidden by default, but exposure button is provided in each NB assemblage) an <F10> will focus onto main menu. With <F6> available to move between UI regions. The <Alt> key then will expose the mnemonic accelerators of the menu controls and functions in those keyboard sequences. As should be obvious, in that context the <Alt> key is already allocated and is not available to further overload for movement onto the NB Tabbed assemblages--just for the Windows builds. The LibreOffice Notebookbar is not the MS Ribbon API. IMHO => WF
(In reply to V Stuart Foote from comment #1) > That is keyboard movement onto the NB's UI > elements is via an normalized <F6> focus event onto the NB, the active "Tab" > will highlight. F6 might access the NB but tabs are still not available for quick access, while mnemonics are visible (Qt). Accessibility is a major blocker for making the Tabbed Notebookbar the default UI (bug 135501), and this particular issue is known for a while. => DUP *** This bug has been marked as a duplicate of bug 107344 ***