When left mouse is pressed on contact applet in tray, cursor focus is set to "Search Contact" editbox, so you can immediately start typing. But when shortcut is set to activate contact applet, you have to press tab key to set focus to editbox. I think it's small thing, but nice feature to have ability to search right after shortcut key is pressed. And of course I am using KTP 15.12 with Plasma 5.5.2 Reproducible: Always
Was going to raise the same. It looks like a small fix but would increase usability noticeably.
Actually, well, I had already raised the same at https://bugs.kde.org/show_bug.cgi?id=353684 :) This can be closed as duplicate.
*** This bug has been marked as a duplicate of bug 353684 ***