Currently Pixelmator Pro's automator Scale Images action appears to fit images to a specific set of pixel dimensions (defaulting to 640x480), offering the option to scale proportionally. Unless I'm missing something these options are somewhat lacklustre.
It would be much more useful if the Scale Images automator action behaved a lot like Pixelmator Pro's in-app Image Size UI, providing options to scale in terms of pixels, percent, inches, cm, mm and points. The option for resampling and resize algorithm (Bilinear, Lanczos, Nearest Neighbor) would be most useful too.
Note: Currently using Pixelmator Pro 1.8.
What features would you like to see in Pixelmator Pro?
I'm not sure if we'll be this option to Automator but we've already made it possible using AppleScript! If your workflow is mainly focused around Automator though, you can convert the scripts you write to Automator workflows and combine them with other actions.