That’s not what I meant… I meant using the Amplify effect or the volume slider to the left of the waveform. But you can use the envelope tool if you want to fade-up or fade-down certain parts. (That kind of thing is probably easier in Cubase or other DAW.)
ReplayGain (and these other’s) aren’t “levelers”. The intention is adjust the volume of the whole song (or a whole album) buy adjusting the volume of each song before before the song starts. When used as intended, a song that starts-out quiet and ends loud retains those dynamics… Just one adjustment for the whole song before playback starts. (And in album mode one adjustment before the album starts.)
how do you export just one section/piece of audio rather than the whole project?
Maybe I don’t understand what you’re doing… Export Multiple is one way. You can also select/highlight a section of audio and then Export Range: Current Selection in the export window.
Final thing, when you import multiple audio files into an Audacity project it seems to put them on different tracks.
You should get multiple files. You may need to re-import them (Import, don’t Open). Then, they will be on different tracks in the same project and you can drag them to the right to sequence them. (Drag the track name above the waveform).
When you play or export they will be mixed (to stereo or mono). But if they are sequenced so they don’t overlap you’ll be mixing with silence and they will play in sequence.