I recently migrated my Windows installation to a Samsung m.2 drive. Since the capacity for those drives is expensive, I want to keep any unnecessary files off it.
Using TreeSize (free) to check for large directories and files, I noticed that Spotify was storing over 10gb of files in local app data with no option in the app to choose a different location.
That's when I discovered that Windows 10 actually has a command to create symbolic links and directory junctions!
To solve the problem:

• locate the Spotify storage directory (mine was C:\Users\Jiko\AppData\Local\Spotify\Data) and delete it


• create a new directory where you want to put Spotify's data (mine is D:\Spotify\Data)


• open a command prompt  (windows+r)


• create a Directory Junction

mklink /J "C:\Users\Jiko\AppData\Local\Spotify\Data" "D:\Spotify\Data"

Spotify won't know the difference and your hard drive will be free :)