Or... work around of the week.
Imported frames IE "sprite load animation frame from file" generate a collision mask. Even if said frames have no alpha, and use "magic pink" instead.
How is this useful?
Images like this:
Can be imported and used as an obstacle mask for rts, solid etc.
Why should you care?
The image manipulator object does not have options for an alpha channel, and while "magic pink" does work for making an alpha, a new mask is not made unless its imported.