Upon starting some playlist, you would normally keep on browsing through artist pages / albums etc. , but there is no means to easily get back to the playlist your are currently playing! This creates a lot of hassle, when your only option is to "go back" until you finally reach that playlist from before.
You can return to the current playist or album you are playing. On desktop you can do this by clicking the album cover in the lower-left of your screen. You'll need to click the lower-left part of the album cover so you don't expand/minimize the image. That will take you to the current list of songs playing.
On mobile you can return by going to the Now Playing screen and then tapping the title in the top of your screen.
Hope this helps! Let us know if you have further questions.