Automation Blocks - Batch export stills using clip in point instead of markers

I've just discovered the plugin Automation Blocks and it seems to be the perfect tool to solve a very specific problem I'm having: I'm using titles as VFX markers and I'd like to be able to batch export stills of each VFX shot. The "Render Frames at Markers" seems like it's very close to what I need, except I need it to use the start of each clip on a specific video track to pull the frame instead of markers.