I was recently editing some audio in which short sections needed turning down. So that I could come back and redo it if needed, I stored the areas selected as labels, which I can export to save me having to save a project. A few things cropped up:
In particular it would be of great benefit to have a live snap-to-zero-crossing. The current Z function proved to be a bit unpredictable.
When adjusting labels it would also be useful to have some indication, like a vertical line, of where you are on the waveform.
Apart from that, Audacity was just the job. I especially appreciated the ability to split stereo files quickly.
This does not fully answer your questions, but may be some help:
Snap to zero crossings will always be a bit unpredictable with stereo tracks as there may not be zero crossing points in the same place in both channels.
If you are using region labels, click in the label text area. This will highlight the region of any selected audio track(s). If you then adjust the label with your mouse, as soon as the label is released the selected region will move to the new label position.
For point labels it is sometimes easier to delete the original label then click on the audio track at the required new label position and create a new label (keyboard shortcut: Ctrl+B)
I should have mentioned it but the snap to zero was on a split stereo (hence mono) file. It’s not wildly unpredictable but I would find it much easier to work with if the snap was live.
As for the selection area, it does indeed move when I release the mouse but that still leaves me having to guess where I’m at and when I’m trying get tight to the beginning of a kick drum, say, it’s a little fiddly doing it this way. Perhaps if there was a live snap, then it wouldn’t be so tricky, or if the selected are moved with the label.
I agree that it may be better to delete the old label and create a new one (as I have done sometimes) but I still miss the snap.
Another tip that may help - taking the case of labelling precisely from the start of a drum beat:
If the label track is not directly below the track that you want to label, drag the tracks into a new order so that it is. Tracks may be dragged into whatever order you want.
Zoom in really close on the start of the drum beat (If you have a mouse wheel, try using Ctrl+Mouse Wheel)
Left click at the precise point where you want the label, or end of region label in the audio track - this will put the playback cursor at the point where you click, which is visible as a vertical line on the audio track.
Adjust the label so that it lines up exactly with the playback cursor (the vertical line on the audio track).