IMHO Matroska is one of the best video container, so i dlike to crete my movies in this standard. Kdenlive can render movies iny many other formats but I can't see matroska on the list.
How to do this?
PS. sorry for my english :)

If you are familiar with ffmpeg args you can create your own profile for matroska in the render dialog. Unfortunately I'm not.

You need to decide which codecs you want. Then, pick an existing render profile that best matches your codec and bitrate selection. Next, make a custom copy of that profile and change the filename extension and 'f=' option to "mkv".

ok, but when we show the native support for writing file in mkv? Matroska is one of the most popular container. In my opinion mkv profile should be add in new version of Kdenlive.

Any news for a new upcoming version?

I have tried to add "f=mkv" into rendering profiles but then I get error "Not supported Videoformat: mkv"
(kdenlive 0.9.2 on debian wheezy)

markinfo, try f=matroska ;-)