Tool to move clusters or to alter timestamps in MKV files?

[Unforgettable]

Hello everybody,

the whole story is too boring and too long, so I'll get to the point: Does anybody know of a software tool that lets me carry out at least one of the following actions?

1.
Alter the timestamps of clusters in a MKV file, and the timestamps of frames that belong to a certain track? That would be bulk manipulation; for example, I would have an input file that contains the timestamps of all frames from a certain track, and those frame timestamps should be altered accordingly.

2.
Move one certain cluster in a MKV file to another file position (file offset) without altering anything else, notably without altering timestamps; I wouldn't mind if this would involve copying the file.

Thank you very much in advance for any ideas, and best regards.