Is this issue being seen with hitboxes or component events? If so I fixed that just after 4.1 was branched. You can see the fix here: https://github.com/EpicGames/UnrealEngine/commit/eda97cbd2a6dd6b741951d25c6d62ef7efddda2f
The UIInteraction ini settings are old legacy. Apologies for them being there, I’ve just removed them.
The mouse double click delay is generated by the operating system and for the rest of the keys (like double clicking space) that is in BaseInput.ini in the Engine.InputSettings section (and editable through the project settings UI).