SUMMARY

Sometimes it is useful to know the length of, at the very least, the current playlist. I use it to estimate the amount of time I would've spent working on something else once the album ends.

Amarok appears to have this feature judging by Bugzilla's automatic duplicate search, and Spotify also has this feature which is how I became aware of it.

STEPS TO REPRODUCE
1. Play an album or an existing playlist

OBSERVED RESULT
No way to find the total length of the playlist other than adding up individual track lengths manually

EXPECTED RESULT
Total length of the playlist shown somewhere in the interface for the current playlist

SOFTWARE/OS VERSIONS 
Operating System: Manjaro Linux 
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.106.0
Qt Version: 5.15.9