This scaling problem in Adobe Muse is encountered when you set Windows Scale settings to 125%. Adobe Muse renders its user interface at 100%, 150%, or 200% depending on the Windows Scale settings and the environment variable. If the environment variable is not set and the Windows Scale setting is set to 125%, then the Adobe Muse user interface displays at 150% resolution.
If you prefer to keep your current Windows Scale settings, you can set an environment variable to force Adobe Muse to render its user interface at 100%.
Windows Scale settings impact the overall Windows screen display. You can add Environmental Variable value to control only settings for Adobe Muse and not impacting the overall Windows display.