In case someone has updated Windows 10 to their latest update (Creators Update) and is still using Unreal Engine 4.13, here is a useful post regarding the drop-down menus:
To sumarize, you are left with the following options:
use the "-opengl" flag on your executable
use the "-D3D12" flag on your executable (worked for me)
download the engine from the github, make a one-line change and re-compile (this is a hack and might brake something else, therefor it is not recommended)
migrate the project to a higher version of the Unreal Engine (painful, lot of work)
revert back to the previous version of windows (probably better to reinstall the Windows all together)
In case someone has updated Windows 10 to their latest update (Creators Update) and is still using Unreal Engine 4.13, here is a useful post regarding the drop-down menus:
https://answers.unrealengine.com/questions/483838/editor-right-clickdrop-down-menu-invisible.html#answer-484658
To sumarize, you are left with the following options: