Tokøta from Mastering.com walks through Logic Pro's Scripter MIDI effect using the Guitar Strummer preset, which turns single held notes into full chord-based strums and arpeggios.
Playing one note at a time (C major, A major, D minor) triggers layered arpeggio patterns with varying velocities, controlled by adjustable divisions and velocity curves.
The generated pattern can be recorded straight to a MIDI track, quantized and cleaned up, then used as a composition starting point even after Scripter is turned off.
It won't sound like a real guitarist, but it's a fast way to sketch strum ideas, whether to build a demo or hand off to a session player for the final take.