Control surface and source monitor
When using a control surface, one is able to change the levels while previewing clips in the source monitor, just as you are able to do with your mouse.
However, when doing this with a midi control surface, the volume data doesn't port to the timeline. Once you edit the clip onto your timeline, all the levels are back at 0. This only works with the mouse. My workaround is to ever so slightly manipulate the levels in my source with my mouse after I've done so with my control surface.