I chose "technical," then "other," the kept clicking "I still need help." Eventually you get a message window where you enter a description of your problem and email address. This established a direct line to Spotify via email.
This issue has been escalated. The upshot is that their development team could use more input from users across various operating systems and devices in order to track the source of this folder bug. The more people that contact them, the faster a fix will be. In this instance you don't need to go thru the help URL, as the path has been made. Here's what to do:
1) Email Spotify directly at: firstname.lastname@example.org
2) In the subject field copy and post either discussion thread title:
Collapsing/expanding folders make items in the sidebar disappear. or Spotify playlists & folders missing when I expand folders?
3) In the message body state that you are experiencing the problem discussed in
4) Additionally, list whatever actions you have tried thus far so they don't recommend things you've already done. They will respond quickly. At that point they will ask for device info so have that on hand.
This seems to be the most helpful thing we can do at this point. I am sick of working around such a broken interface.
Checking back in 2 months later after my original reply and still no solution? This is making me start to question my Spotify brand loyalty for the first time in probably 10 years. Can we please get another moderator in here to at the very least make us feel like we're being heard?
I attempted the clean sweep reinstall that Katerina replied with 2 months ago again this weekend (for the second time), and the issue happened immediately on the first attempt to open a folder.
For what it's worth, I accessed the Spotify tech support via the user's directions further up in the thread. Tech support was responsive and data was gathered. I feel that this is in fact a problem in the code with Spotify, it simply hasn't yet received the attention it deserves. I suggest reaching out to tech support. Be prepared to have screenshots and screen recordings ready.