You can now add multiple grouped stacks to Photo Merge queue by the keyboard shortcut: CTR+SHFT+H. However, wouldn't it be incredible if we could just select multiple grouped stacks and add them all to the photo merge queue at once? I work regularly with HDR and once a month need to deliver 400+ HDR images. It takes me two days to just get them in the photo merge queue. If I could select them all at once and add them to the queue, it would save me so much time!