The 'Patlock' is a neat solution for french doors (google it), is there a similar product for a bifold door where the leaf with the handle is adjacent to the wall?
Something as simple as a bracket attached to the wall to prevent the handle from rotating downward would do the job, wouldn't it?
You can get door braces to prevent a door being pushed open but that doesn't work on i) outward opening or ii) a multipoint locking handle where you can lift the handle up.