Currently, there is no shortcut for Search and Replace. I suggest to use "Ctrl+Alt+F" which is still free and which is also used in kdevelop for the same function.
You can assign the shortcut you wish for the Search and Replace panel. Also, Ctrl+R will show the simple Replace.
Thanks for the hint. I rephrase the suggestion: "There is no _default_ shortcut for the search within all files or projects. It feels arduous to tell each new user to manually assign a shortcut for this commonly used feature."
Patch adding Ctrl+Alt+f here: https://phabricator.kde.org/D4796
Git commit 26308a744ee094aff19617ee890f0f56086459e8 by Dominik Haumann. Committed on 26/02/2017 at 16:08. Pushed by dhaumann into branch 'Applications/16.12'. Add shortcut (Ctrl+Alt+f) for Search and Replace FIXED-IN: Applications 16.12.3 Differential Revision: D4796 M +1 -0 addons/search/plugin_search.cpp https://commits.kde.org/kate/26308a744ee094aff19617ee890f0f56086459e8