RelaxChess 7 is ready and available in Windows strore https://www.microsoft.com/store/apps/9NF45RD240HN.The new engine is built in C++ (DLL) and GUI executable in Universal Windows Platform (C#). Comparing to older (C#) chess engine versions , the new one is about 3-4 times quicker. The chess engine is single-threaded in lower modes and multi-threaded playing in Expert mode where engine searches deeper looking for a good move.
There are also many GUI improvements including new themes. Try it out.