Thank you, i do not know why, but mkvtoolnix shown that i am using version 5x and 63 is available. Then i have tried to reinstall as you have suggested:
$ sudo pacman -S mkvtoolnix-gui
it found: :: mkvtoolnix-cli and mkvtoolnix-git are in conflict. Remove mkvtoolnix-git? [y/N] y
full output
then i have removed the symlink i have created previously: sudo rm /usr/lib/libcmark.so.0.29.0
and mkvtoolnix launch without issue, in latest version 63. I do not know what i did wrong that it was corrupted, maybe manjaro can prevent or be more informative to the noob user like me - seems like i was running two versions at once and some outdated was silently preferred.