When working with Indesign CC2018 and still in CC2019 on Mac. I can't use the Toolbox/bar on my second monitor connected to my MacBook. When the Toolbox is placed/locked on to the left hand side of the screen, the submenus of all tools (Type, Pen, Pencil etc.) don't open on my secondary monitor, but semi randomly are placed on the display of my MacBook. the only way to "fix" this is to place the Toolbox on the MacBook's display, but that's not the way to go about it...
It has something to do with different resolutions of the two screens, the tool submenus (if the toolbox is docked to the left side of my monitor) get placed outside of the viewable area of the MacBook display. if I place the Toolbox in the middle of my monitor, the tool submenu is placed a certain amount to the left of the toolbox.
Strangely enough, Photoshop and Illustrator don't suffer the same problem.