Why is it that some tracks will allow opacity (video) and gain (audio) adjustment by dragging the opacity/gain down within the track on the timeline, and others won't?
You can't adjust opacity or gain of tracks that way. You can only adjust events. Is there a chance that you're doing this inside an event on the "tracks" that work and in empty areas of "tracks" that don't work?
Okay, let me rephrase the question. Bear with me, I'm still a noob.
Within some tracks, I can place my mouse curser at the top of a video clip or a picture or a sound bite, and the pointer becomes a little pointy hand and I can drag the opacity (or the volume) down. In other tracks I can not do this to pictures and sounds.
So my question is, why is it that pictures, sounds, and video clips in some tracks are adjustable in the manner described above, and in some tracks the pointer will not change into a hand when placed at the top of the sound/clip?
My guess is that someone or some thing has Locked some of your events.
Events that are locked cannot have their Opacity (or Volume) envelopes (or anything much else) adjusted. (This is so tnat once you've got them right you can prevent them from being accidentally changed.)
To see if this is correct, right click on one of the events, choose Switches and see if Lock is ticked - if so, untick it and you will be able to adjust the envelope again.
(Locking applies to Events rather than Tracks, but I'm guessing that when you say this problem occurs on certain tracks but not on others you are incorrectly deducing this when it actually applies to certain Events and not others.)
If this isn't the reason, and it truly is some Tracks and not others, then I'm mystified.