I have the EXACT same problem as the OP from the post below. I have a Border in my UMG and I use “IsInputKeyDown” “Left Shift” in the OnDragDetected-overridden-function. But it only detects it when I press it the second time. Even if no other keys are being pressed:
https://forums.unrealengine.com/development-discussion/blueprint-visual-scripting/93571-is-input-key-down-in-widget-issue
The node suggested here by the staff member (EnableInput) does not exist for UserWidgets, only for regular Blueprints: https://answers.unrealengine.com/questions/19063/input-keypress-does-not-work.html
I could not find a solution anywhere. How is this done?