Wow, this is an old topic:)
It’s possible that this may be added at some time in the future. The downside is that projects may become extremely large (they already tend to be big).
That doesn’t have to be the case - only so if we save the full undo history.
We could just save a history list of all effects that were applied along with the parameter settings used. That shouldn’t take up too much extra space.
Such a list could even be exported and used as the starting basis for a Macro 
Or for QA testing purposes on new alpha test builds and RCs 
Peter.
Gosh this is an old topic! It’s 2023 and I’m still searching for this same functionality. How big would the text file be? Not very big, I reckon. If it just saved the last 1000 edits, with an average description length of ~1000 characters per logged project step, that would lead to a project log file of ~1MB.
I do love Audacity, and I have huge respect for those who made it. Also, I would also love to see this feature!
Once all effects are converted to real time, this will be moot.
As for saving “the last 1000 edits”, just saving a text file describing each edit is useless without a history of the audio that was modified.
The brute force approach would be a user option to save the undo history with the project, but then projects could quickly explode to 10s or 100s of gigabytes.
Oh, no, I’m not interested in being able to undo - just reproduce a sequence of effects using the exact same settings, so a later recording can be matched to a previous one