Artwork and Visuals

Icons (added tons of icons to the Breeze theme, plus reworked the Systray

icons to match the general theme)

Breeze widget theme
Look & feel / Megathemes KCM
Plasmoid alternatives switcher
Klipper Plasmoid
System load viewer Plasmoid
HIG restructuring to improve usability (not exactly a Plasma feature, but

since Gnome promoted their new HIG with the 3.14 release...)

Visual glitch fixes

Workspace Elements

return of kwidgetaddons (notes, fuzzy clock, timer, system load viewer, icon tasks)
return of the timezones
a tonne of runners
plasma windowed (if it can be presented as not just an implementation detail)
Notifications have improved look, some new features too (like not showing Open button for finished jobs when there's nothing to open)
Calendar has way improved grid rendering
Date in the clock (initially done by Dan Vrátil)
Logout screen now handles "Return" key properly

Folder

Significantly improved performance and memory usage in desktop mode.
Faster, more responsive DND operations.
Greatly expanded context menus.
Support for the 'associated application' system is back.
Keyboard nav improvements (support for Home and End keys, etc.).
Spatial keyboard navigation (arrow keys, etc.) for unsorted views.
Tooltips can be disabled.
Icon size can be changed (disabled it shortly before 5.0 due to a bug).
Better guard against corrupt config.
Many bug fixes (a few bigger ones: graphical glitches with DND on some

drivers addressed, sort by size was broken, anchored range selections on unsorted views misbehaved, drag-onto-to-launch for view-internal DND crashed didn't work, ...).

Some platform fixes that show up here the first time, e.g. the view

context menu now works when Folder is a panel popup.

Kicker Application Menu

Basic support for editing menu entries right from the context menu

(name, icon, command, etc.).

Per-instance hiding of menu items.
Basic integration with Muon Discover / package managers via

PackageKit-Qt (you can jump into them via the context menu).

Support for screen readers and other a11y software.
Various bug fixes (a few bigger ones: improved positioning, "Add to

Panel" with multiple applet instances in different panels could pick the wrong panel, initial keyboard focus when invoked via shortcut wasn't on the search field, ...).

Task Managers

Icons-only Task Manager is back. ("Icontasks")

- Improved lifecycle behavior for launchers and startup notifications (clean handoffs/replacing, less visually messy co-existence). - More reliable identity mapping between startup notifications and launchers and windows.

Search

A user visible query language which can be accessed via the kioslave. Example - `baloosearch://?query=tag:Fire`. The query language can handle quite complex expressions. This will create a "magic folder" which will be updated in realtime
Better UTF8 handling in Searching - We now take diacritic marks into account. See relevant blog post
Removable Media Storage - We now never index Network File Systems.
Better detection of frequently modified files. We delay indexing for them.
Detecting xattr changes - Baloo is now more of a file indexer and will listen to changes on xattr for files. This means any application can set the tags/ratings by just setting the xattr of the file. Applications no longer need to talk to Baloo.
Overall speed improvements
Many more tests in the File Indexers

Compositor and Window Manager

Wayland Support

new binary kwin_wayland
kwin_wayland supports starting the X-Server it needs to connect to
Wayland (client) connection is hold in a thread
Support for using fullscreen shell interface
Wayland related code split out into a new kwayland lib

General

use of libepoxy
use of atlas texture for window decorations in OpenGL compositor
support for EGL_EXT_platform_x11 and EGL_EXT_platform_wayland
support for GLX_INTEL_swap_event in glxbackend