It takes 4 taps to go in to offline mode, and another 4 to get back to where I was (and by then have lost my place in the scroll). Logically, I'd just tap the words at the bottom of the screen that tells me which mode I'm in to toggle the mode.
Even better would be an automatic offline mode when wifi is unavailable.
I'm using iOS 8 on an iPhone 5C
A similar has already been suggested. Please add your kudos and support there. https://community.spotify.com/t5/Live-Ideas/Mobile-Make-Offline-Mode-toggle-easier-accessible/idi-p/...