https://mkvtoolnix.download/
(Offical download page for this app is this: https://www.fosshub.com/MKVToolNix.html)
"MKVToolNix is a set of tools to create, alter and inspect Matroska files under Linux, other Unices and Windows."
This app has been around for ages, (since 2003) is known and is still regularly being updated. Free and Open source. MKVToolNix is being offered as installable and portable versions. I'm requesting for an installable one.
(I tried to add this request here: https://patchmypc.net/vote-for-new-apps but I received a notification that a website firewall has blocked my attempt.)
It's in the poll now, Don't forget to vote for it!
https://patchmypc.net/vote-for-new-apps
And sorry about the firewall block issue, we will look into this :)
This app has been added and will be available very soon in the next release of Patch My PC :)