As far as I’m aware you have no control over reverb (or lpf) in the soundcue editor. It is something that has always bugged me, as it is clearly supported in the engine.
You have to rely on using Reverb volumes (and distance to control lpf).
I ended up doing some pretty hacky things to simulate lpf when moivng in/out of shelter. Basically playing ambient sounds on an actor attached to my local player, then controlling it’s range from the player to bring in/out lpf effects using the attenuation settings.