For a millisecond display, the update frequency of the UI timer would have to be increased significantly to make any sense (otherwise the last two digits will always just be 00 and that makes about as much sense as the inflated scoring system in pinball machines ;)). I'm not sure if that's a good idea given the load it adds to UI update tasks, and especially with smooth pattern scrolling that might make it even easier to completely lock up the UI. Adding a 1/10th-second display would be more realistic.

This could make more sense (and be way more useful) if the displayed timing would be tick-aligned. However that is currently not possible.

In r21114 I have increased the precision to showing 1/10th seconds. As mentioned above, it currently doesn't make much sense to increase the precision beyond that. As a side effect, the active channel count is now also updated more frequently, which is more similar to Impulse Tracker (I was always a bit annoyed by the low update frequency so I consider this to be a positive side effect).

You can download an updated test build from https://builds.openmpt.org/builds/ (will take a few hours to show up there). Please let us know if this change is satisfying enough for you or if even higher precision is still needed.