When you use a parameter as an item, parameter selection window has confirm button and E shortcut works.
if you want to paste a blueprint with parameters which is used as a fluid, then parameter selection windows doesn't have the confirm button. E shortcut also doesn't work.
I think it's because fluids doesn't have quality, the whole section is removed when trying to hide the quality buttons.
[Kovarex] Fluid parameter selection window doesn't have confirm button
Re: [Kovarex] Fluid parameter selection window doesn't have confirm button
Yes, no confirm is required when quality is not selected, it is a feature, not a bug.