Feature Request - Export Captions Below Image (Bitmap Export)

Hi, I was wondering if there are plans of adding an extra option when exporting to bitmap.

I think a lot of people would benefit if it was possible to append a black/white box BELOW the image with the captions (as usually seen in storyboards made in Photoshop), thus extending the height of the exported image.

Example: Original Image: 1920*1080

Modified image with captions: 1920*1280