When the new Photos app appeared in Yosemite, it did not support direct drag and drop into a FileMaker container as iPhoto did. Fortunately, in iPhoto was not deinstalled in exiting Yosemite updates but is not present on new computers.
It is a reported issue.
I was surprised that FileMaker drag and drop doesn't seem to work in FileMaker 14 either (in either El Capitan or Yosemite) as this is a key Macintosh kind of behavior.
In reading about Photos drag and drop, it appears that the Apple Photos Developers are taking a position that other software providers will provide this functionality as an extension (i.e. FileMaker needs to enable it . . . I might be wrong as I see this stuff on Apple forums).
As a workaround, we download iPhoto to our customer computers but it causes confusion as to which photo viewer is in use locally and with iCloud. There is always the Dropbox photo sharing feature, which also works.
But each Mac comes with Photos and it should work well with FileMaker. (I won't belabor the whole 'same company' thing).
Any updates? It is very hard to explain to our mutual customers.