It could be very useful if KDevelop's documentation viewer had the possibility to open a regular window that can be stacked freely (= covered by the KDevelop main window) and that also remains visible when KDevelop doesn't have focus (for instance to compare with documentation viewed in a web browser). Qt Creator and Xcode both do this, and it is much more convenient than having to start an external viewer like Qt's Assistant, or having to move a pesky utility window around (restacking can be done with keypresses, moving windows much less so). It would of course be crucial that the settings related to such an option are saved and restored reliably (including the viewer window size and position, IMHO).
Good idea to propose this as a junior job - had I known that I would have proposed to enable something similar for the code editor tabs (like in Xcode where you double-click an entry in the project explorer or an editor tab to open the file in a regular window).
Created attachment 103828 [details] using Qt's assistant as an external viewer This is just for illustrational purposes. I've been digging through the documentation plugin sources on a (fruitless) hunt for the explanation of an issue that's been getting under my skin. I whipped up the attached patch as a by-product. It illustrates a very basic implementation of an external help viewer, using the remote control interface of Qt's Assistant if that utility is accessible via a symlink or proxy called "kdevelop-qthelp-viewer". It maintains a single Assistant instance per session at most, and terminates the instance when quitting the session. The Assistant is well-behaved enough not to unhide and raise itself when minimised/iconified/hidden, so this feature actually works pretty neatly (admittedly on a large screen or multi-head set-up).