Instead of downloading/extracting the youtube audio and then trying to split it based on the separate list, one should consider that such music-video files may have chapters, with a separate chapter for each track (as the file in question had).
There is a youtube-dl fork that has an option to download the chapters separately (in fact it downloads also the full audio and then splits it).
It is called yt-dlp.
In order to download the best m4a audio in separate tracks:
yt-dlp -f ba[ext=m4a] --split-chapters URL
In order to first list the available formats:
yt-dlp -F URL
which gives something like:
[youtube] QsmFrf-1wYE: Downloading webpage
[youtube] QsmFrf-1wYE: Downloading android player API JSON
[info] Available formats for QsmFrf-1wYE:
ID EXT RESOLUTION FPS CH │ FILESIZE TBR PROTO │ VCODEC VBR ACODEC ABR ASR MORE INFO
──────────────────────────────────────────────────────────────────────────────────────────────────────────────
sb2 mhtml 48x27 0 │ mhtml │ images storyboard
sb1 mhtml 80x45 0 │ mhtml │ images storyboard
sb0 mhtml 160x90 0 │ mhtml │ images storyboard
599 m4a audio only 2 │ 14.00MiB 31k https │ audio only mp4a.40.5 31k 22k ultralow, m4a_dash
600 webm audio only 2 │ 17.51MiB 39k https │ audio only opus 39k 48k ultralow, webm_dash
139 m4a audio only 2 │ 22.18MiB 49k https │ audio only mp4a.40.5 49k 22k low, m4a_dash
249 webm audio only 2 │ 25.65MiB 56k https │ audio only opus 56k 48k low, webm_dash
...
and then download the desired audio format while splitting per chapter:
yt-dlp -f 139 --split-chapters URL
Source: here, here and here.
In order to automate that a bit, I have installed xclip
. A shortcut can trigger the whole process (first selecting url, then using the shortcut) with a command like:
konsole --noclose -e yt-dlp -f ba[ext=m4a] --split-chapters $(xclip -o)
Or a desktop/panel launcher can be created, containing the same command:
[Desktop Entry]
Exec=konsole --noclose -e yt-dlp -f ba[ext=m4a] --split-chapters $(xclip -o)
Icon=im-youtube
Name[en_US]=Download youtube chapters
Name=Download youtube chapters
After dragging it onto the Plasma panel, just select the URL and click the button:

UPDATE on Plasma: in Plasma KDE, xclip
is not needed in fact, if the clipboard actions are used. More details in my related answers under here and here.
.cue
file with time stamps, and aflac
master file with all the tracks? Tryflacon
(https://flacon.github.io/download/) – Jos Sep 13 '22 at 15:06