: Adobe rebranded Flash Pro as Adobe Animate in 2016. Animate includes a native dark mode that you can toggle in Preferences > Appearance . If your hardware supports it, switching to Animate is the most stable way to get a dark interface.
Help you find to Flash that have native dark mode. adobe flash cs6 dark mode link
Be careful. Many YouTube videos provide links to .reg files claiming to give "Full Dark Mode Flash CS6." Most of these only change the timeline and panel headers to dark gray, leaving the stage properties and library windows white. They do not change the actual document workspace background (that is saved per-file). : Adobe rebranded Flash Pro as Adobe Animate in 2016
If you find a working link to a patcher (like the flashcs6_darkmode_v2.zip floating on archive.org), treat it like the fragile artifact it is. Back up your original Flash executable first. Because when that patched UI finally loads, and you see your onion-skinning against a soft black background, you realize the truth: Help you find to Flash that have native dark mode
Adobe Flash Professional was rebranded as in 2016. Animate is included in the Creative Cloud suite and features a fully native, customizable Dark Mode UI that matches Photoshop, Premiere Pro, and After Effects.