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 kicking and screaming into the present day. Here's the cliff notes of the todo:
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. :)