If you bind a widget’s tooltip field to either a text variable or function, the tooltip will show an empty value ingame unless you also put a temporary default value in the tooltip field at design time, in the UMG editor.
This was tested on UE4 4.7.3.
Hello Bugfoot,
I was able to reproduce this issue on our end. I have written up a report ( UE-13264) and I have submitted it to the developers for further consideration. I will provide updates with any pertinent information as it becomes available. Thank you for your time and information.
Make it a great day