One of the biggest peeves when working with LibreOffice (something I do every week, even almost every day), is the confusing and poorly designed Area Fill workflow. If you've worked with LibreOffice (especially Impress or Draw) for long enough, you've probably run into (and gotten frustrated) with this. Applying gradients is probably one of the most frustrating areas of "Area Fill" (pun intended).
Thankfully, plans are underway to make the workflow more consistent with that introduced in the sidebar, and to simply editing/creating new gradients, hatches, etc. You can see more on this here, though I must say, from the mockups, there will still be a need for user feedback even after the changes, in order to simply/polish the interface further.
Perhaps one of my favourite changes to LibreOffice in recent years has been the introduction (in LibreOffice 4.1) and continual improvement of the sidebar, which was inherited from IBM's Lotus Symphony.
However, as with any new or imported feature, there is (almost) always room for improvement. One of the planned improvements to the sidebar is the addition of a "Shapes" tab, which will bring LibreOffice a little closer to usability parity with its close (open source) competitor "Calligra" (though, honestly, LibreOffice is miles ahead in most areas, including, in many aspects, usability).
There is a poll (which will influence the default shapes included with LibreOffice) included in the link concerning the Shapes tab, so please vote if this feature interests you!
Saving the best for last, the "Extended Toolbar" feature builds upon the ongoing work to port the LibreOffice interface to glade so as to improve the workflow for interface programmers+designers. From the description, it seems like this work could lay the foundation for a massive overhaul to the LibreOffice interface in the future, including dynamic layouts, and - possibly - a move to a "Ribbon-like" interface (tabbed toolbars).
NB: These are not the only LibreOffice projects planned for the GSoC. As more information becomes available, I'll post about any notable or especially interesting news that I can find.
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