[Cannot select open images for HDR, Stack, Panorama, etc]

One thing you can do while you wait. (for Mac only)

1. Open Affinity Photo
2. Open Capture1 and select your 3+ files for merge
3. Switch to Affinity Photo:
   1. Open the Stack, HDR, etc dialog
   2. click the Add button
4. Drag the three + images from Capture 1 over to the Mac's file browser (what opened in 3.2)
5. That should switch you to the right dir and select all of the files. Now just accept and continue.

I agree that a native drag/drop would be better, and even better would be a plugin for C1 that leverages their new plugin architecture. I believe the Affinity Photo/Capture One is the one two punch to the Adobe empire, let's make it awesome!