You can customize Spine's hotkeys by updating the hotkey text file!
Let's say we wanted to add a hotkey for the "bind" button for example...
Go to Spine > Settings > Application tab > and open the hotkeys file.
In the notepad window that pops up, ctrl+F to open the finder, type "bind" and it will take you to the correct spot.
You can do something like "ctrl + alt + B" to add a hotkey (or whatever you want, just be sure to search the file first so you know there are no duplicates)
Restart Spine and it should work when you have an image attachment selected!