Product and version: FMPro Advanced 16.03
OS and version: Mac 10.13
Hardware: MacBook Pro and Apple Cinema Display
Description: window resize always calculates off of the laptop display, not the external monitor, even when the window is opened or currently located in the external display. in apple preferences/displays/arrangement, the relative "top" of the laptop to the relative "top" of the external monitor influences up/down window movement. left/right is always calculated from left of primary display, even when laptop is to the right.
How to replicate: open filemaker pro on a laptop with an external display. compare moving a filemaker window with the laptop positioned on the left, versus the right of the external display. now move the laptop up and down relative to the external display in preferences, and see how the position is always determined off the laptop
Workaround (if any):
left/right: keep the laptop to the left of the display (doesn't work for my office configuration) or write complicated script workarounds to check for external displays (this is what i've done).
top/bottom: keep the top of the laptop window parallel with the top of the external display window (annoying to be restricted to this, but that's what i've done)