Hello - After correcting audio level , how to eliminate option and come back to normal assembly line . Thanks
If the project is still open in Audacity you may be able to Edit → Unto.
How did you “correct” the level?
Linear volume adjustments, such as lowering the volume by 10dB, are reversable. Simply amplify by 10dB. (Although, there can be some “theoretical” loss of resolution.) There is no automatic way of knowing what the change was. You have to remember.
If you boost the volume into clipping and export a clipped file, that’s not reversable.
Compression and automatic volume control (or automatic gain control) are not reversable.
I don’t know what you mean by “assembly line”.
Could be you’ve used envelope tool 
to correct levels, and now you want to get back to normal 
Merci Trebor : c’est OK