Created attachment 170942 [details]
LibreOffice has settings for icon sizes for "toolbar", "notebookbar", and "sidebar".
However, I have noticed that even if I set the sizes to "small", the toolbar buttons in the sidebar panels (such as the F5 navigator or F11 stylist) are always shown at regular full/large size. You can even visually notice the difference in size when compared to the buttons on the notebookbar (ex: the Bold button vs the checkmark button in the Navigator in the attached screenshot).
Looking at those widgets with the GTK Inspector, we can see that those toolbars' "icon-size" property was set to "GTK_ICON_SIZE_LARGE_TOOLBAR" no matter what the user's preference was.
When changing the size to small, it should probably set GTK_ICON_SIZE_SMALL_TOOLBAR and refresh those widgets, or whatever it needs to do to compact them without needing to restart the whole app.
It could make sense if were to also reduce a bit the amount of padding between widgets when it does that, but at least (re)setting the toolbar/button sizes should already be an improvement. As it stands, particularly in the Navigator, those three stacked toolbars eat roughly a quarter of my available height for the navigator's contents. I wish the Navigator in particular was a bit more space-efficient in that regard.
*** This bug has been marked as a duplicate of bug 126239 ***