Looks pretty sweet. Maybe that could even be used for MOD subsongs?

Here's an update with that...
www.un4seen.com/stuff/xmplay.exeI'm still not really sure about this stuff. It seems very fiddly to me, especially when there are a lot of cues/subsongs bunched up. I think it could be useful with a long position slider, so that there is more room for them to be spread out, but most skins are currently quite small with short sliders.
This is quite useful but my concern is about the aesthetics. Some skins need a little adjustment to fit this feature (colors, slider block in mask). Maybe an option to add a knob_cue or cue_scaler?
Another thing I thought of : instead of the flimsy 1 pixel lines (which isn't looking quite elegant IMO) could you make alternating colored blocks to represent the changing tracks? Something like this:
Yes, that could be a bit better, but I'm not sure it overcomes the fiddlyness

Right now, when hovering the progress bar, its tooltip simply says "Position". Especially with the new cue markers feature, it would sometimes be nice to know what the actual position in time a certain position of this progress bar represents. Currently, the actual time is only displayed when dragging the progress bar, so could this behaviour maybe also be used when simply hovering the bar while a file is loaded? It could simply show the time or, to be more helpful, something like "Position (1:23)".
One obstacle to that is that it would conflict with a little known feature (I think there may be as many as 1 skin using it

), which is that the current position is shown in the position slider's bubble when a skin doesn't contain a time display area.