There is a Settings section at the base of the Import dialog that has a Layer Selector - however at least on my PC in 5.2.1 it is not working so it seems like we have a Bug / Defect there to look at - In that selector you are supposed to be able to hit Space Bar to pull up the Layer Manager and you are supposed to be able to pick a Layer from your Layer List - but that is where on my Laptop it is broken.
Alan