Windows 10, FileMaker Pro 17 Advanced v18.104.22.168
In both Mac and Windows right clicking on a record respects any custom menu set in place, with only those items available within the custom menus available within the contextual menu. See the first image 'Mac Win Record right click.png' below.
If a card (or floating modal type) window is in the foreground on a Mac, only minimum items are displayed within the contextual menu when right click is used. See the second 'Mac Card Window right click.png' below, which is using a card window on the left for navigation. Only 3 items appear in the contextual menu.
However, within Windows, right clicking on the same (navigation) card as above displays all menu items from the background window, including some particularly dangerous ones. See the third 'Windows Card Window right click.png' below, which is repeat of the above but using Windows 10 instead of a Mac.
We've seen many examples of behaviour with front most windows being affected by the menu sets from background windows, in particular the inability to move from layout mode to browse mode, without clicking close, cancel and then save and enter browse mode, but this example affects usage rather than development.
Both Mac and Windows