This is not only a beta issue, as it started with version 1 of Equalify Pro during the second-to-last Spotify Windows client update, but the problem continues with this beta release (184.108.40.20624).
A couple of years ago, I upgraded to a quad-HD (UHD) monitor, with a resolution of 3840 x 2160 pixels. This was a disaster in Windows 7, as automatic scaling wasn’t yet perfected, but by Windows 8.1 (which I’m still running on the system in question), only a couple of old applications I still use don’t scale properly with a scaling ratio of 200% (which makes item sizes comparable to no scaling on a 1920 x 1080 monitor).
And when Equalify Pro was first introduced, its text and other items were scaled properly. But, as I say, a couple of Spotify updates ago, the Equalify child window was no longer scaled properly, as illustrated by the full-resolution screen shot embedded in this post below.