No use in beating around the bush: Yakuake is currently not in great shape. While the codebase made the jump to KDE Frameworks 5 quite early, it took a long time to get releases out, and the latest still suffers from some annoying, if minor, regressions and bugs. The same is also true for outside code Yakuake heavily relies on - namely Konsole, which unfortunately broke some APIs used by Yakuake, including the one used to invoke the "Manage Profiles" dialog. Meh.
Alongside this there's a more fundamental problem, which is that Yakuake's basic UI code has not aged well. There's some nice things to say about Yakuake's theming system, including a stable file format with unbroken backwards compatibility for more than a decade. But that also hints at the fact that it was designed for systems of that era, and for example can't handle scaling to hi-dpi displays at all.
Fortunately I've been able to secure some honest-to-goodness time over the next couple of months address these problems and thoroughly refurbish the Yakuake codebase, dragging it screaming and kicking into the present day. Here's the cliff notes of the todo:
New UI/theming system.This is the big one. The new themes will make extensive use of Qt Quick, adopting some familiar patterns from Plasma theming, and using the KPackage framework for packaging and distribution. This will get us scaling support, allow for more flexible UI arrangements (finally single-bar themes that aren't a gross hack, for one), window shadows, and more. Support for legacy themes will be retained via an internal compatibility theme; they will show up in the config dialog as per usual.
Fix Konsole breakage.Konsole's embeddable terminal component has been making Yakuake's life harder with bitrot and broken APIs. I'll go in and fix it.
Bugfixes.I'll look into addressing the highest-priority bugs that have been reported against the Frameworks 5 version, including the infamous terminal split focus issue.
Wayland.Yakuake mostly works on Wayland, but there's some X11-specific code that yet needs to be cleaned up.
Unfortunately out-of-scope for now will be the often-desired support for session restore; this will need a seperate campaign. But the above will ensure that Yakuake stays with us long enough to enable one.
Watch out for a Yakuake 4.0 deserving of the version bump some time later this year. :)