Using Audacity, how can I export my selection but across all tracks? Say I only want from 0:30 to 0:50 of my timeline, but all non-muted tracks. Thanks.
Make your selection on one track, then either select Edit->Select->In All Tracks or press Ctrl+Shift+K. This will make the selection across all tracks.
You can then export your selection.
Any muted tracks will not be in the final mix.