The workaround is what I already wrote - you can like local files on mobile (but it's kind of buggy and has been buggy for a very long time).
But still, I don't understand what is Spotify's idea and logic behind this behavior? You can do more on mobile than on desktop? How's that logical that the desktop app has less functionality than mobile? Or that the functionality is not similar/same on different platforms?
Not being able to like local files on desktop while being able to like local files on mobile looks like a bug or missing basic functionality that the developers have overlooked and/or don't care about fixing. Asking to submit an idea or vote for it to get basic functionality fixed/working is weird from your part.
Keep in mind that the app's interface and features vary across devices due to different factors, such as the different operating systems. We're constantly working on improving the app and making it more aligned across all different devices, but there will always be differences.
We appreciate you taking the time to share your feedback with us and we'll make sure to pass it on to the right folks.
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