It is not possible to extend the volume column with more commands or more precise commands (well, there are a few dozen possible values left, but I'd prefer not to touch them without a good reason). In fact I have been juggling with the idea of assigning cue points to samples, which then could be called with the volume column's oxx command - o01 would jump to the first cue point, o02 to the second and so on.

Ooo, i like that idea. After all, we generally know where in the sample we need to offset to (as opposed to offsetting to some random or unknown point), so this would be a PERFECT solution. This would actually be more amenable than my suggestion of reconfiguring an older command (which could "decompatibilize" older tracks that use it).

Wow, if you could somehow implement this, we will both be using this alot. ;)

r4862 (soon available on http://buildbot.openmpt.org/builds/auto/openmpt-win32/ as always) implements sample cue points. Currently they work like this: In the sample tab, right-click the point where you want to set a cue, then choose from the context menu which cue you want to set. Then, use the volume column o command to use this cue. The default cues are compatible to the previous command behaviour.

It's obvious that the current implementation is not perfect yet, especially since you cannot actually see the sample cues in the editor. The related issue 0000659 should fix this usability issue.

Works great, mostly intuitive, but the only thing missing is the line to show the cue points (maybe with the oxx value at the top). It would be great if the cue line was of a different color.

Re-opening to add on this last feature...

No need to reopen and cram everything into one ticket, see the relate issue instead. That's exactly what you want.