Talk about an inauspicious start.
The first step of my workflow is to mix an imported stereo flac file down to mono. In every previous version of Audacity, this was accomplished through the Tracks menu: Mix / Mix Stereo Down to Mono.
This tool is no longer available anywhere I have looked. (And I have spent 30 minutes looking.)
No bueno.
Revert to using Audacity 3. Version 4 has lots of features missing.
No need to go back to the previous version since there’s a way to accomplish the same thing in version 4.0, as follows: Click the ‘. . .’ (three dots) menu on the left side of the stereo track and select “Split stereo to center mono”. That will split the stereo track into two identical mono tracks. Just delete one of them and your stereo track is now converted to mono.
They won’t be identical, unless the “stereo” was dual-mono.
You’d have to mix and render the two mono tracks to achieve “mix stereo down to mono”.
No it won’t. It splits the stereo track into two mono tracks, one for the left channel and one for the right. When you delete one channel (say the original left channel) you are left with just the other channel (say the original right channel).
The rendering would be handled on export, so I guess in that sense it’d work if you don’t delete either channel. The better solution, of course, would be to use a program that just has the feature in question – which would be Audacity 3, or my version of Audacity 4, Soundscaper
Yes, I stand corrected. The stereo tracks I used for testing appeared identical when using the “split to center mono” option. But after reading your reply. I tested some others and did see a difference between them. It’s hard to understand, then, why they removed the ‘mix stereo down to mono’ function in the first place.
Tell me if I’m misinterpreting something, but shouldn’t there be a difference between ‘Split stereo into L/R mono’ and ‘Split stereo into center mono’? I would expect the latter to provide the result the original poster was looking for but they both seem to give the same result. Is this a bug?
The only difference between those two command is that “split stereo to centre mono” pans the resulting tracks to the centre, while “split stereo to L/R mono” pans the resulting channels hard left and right. You could do “split stereo to centre mono” then pan the channels hard left and right and you’d have the latter function.
Yes, kind of redundant.
The “mix stereo down to mono” option is not, technically, “removed”. It just hasn’t been implemented yet but is in the pipeline.
Got it. Thanks for the clarification.
I am eager to move to the new program, but cannot do so without this function, which is literally the first step of my audacity workflow. I am assuming it was pulled because Audacity is now a “non-destructive editor.” Cool, cool, cool. If I had wanted a non-destructive editor, I would have chosen a non-destructive editor. IMO, inherrently destructive functions should have been left alone, perhaps with a little “circle D” icon to differentiate them from their non-destructive counterparts.
In the meantime, my advice to everyone is to stick with Audacity 3 for real work, and check out Audacity 4 now and then. Switch to Audacity 4 if and when it meets your needs.
I can’t be the only person who is utterly sick and tired of ‘upgrades’ that are actually downgrades. Phones, laptops, tablets, apps, programmes, all of them receiving a newer version that has screwed up your workflow.
You’re not. And there’s a term for that: enshittification
And while you get a worse experience, they usually expect you to pay more money and / or shove ads in your face in the process. Which, Audacity is now doing by pushing their Musehub and cloud BS… inside the program. 
Have a look at this YouTube video. I think it’s brilliant.
Which incidentally is the reason I quit working on Audacity and am making Soundscaper now.
I actually saw that a while back. Funny, but at the same time, sad how accurate it is.
Do .aud4 files upload and work directly in Soundscaper?
That explains airvreeething! 
They do. There even is support to recover corrupted audacity projects which audacity itself can’t open.