Try using the FX source buttons on the left hand side (INPUT and X-PAD buttons) - they'll determine what audio runs through the isolator section and into the scene FX. For example instead of using the release fx switch to disengage an echo, turn off the "INPUT" fx source button when you're ready to get rid of the effect and the dry track will return, with the echo tail heard on top.
You can use different combinations of these two buttons to apply any of the effects to different parts of the sound including the release FX - so for example you could apply a vinyl brake effect to just the tail of an echo from the scene fx by turning the INPUT fx source button off before hitting the kill switch. Likewise you could apply the isolator/scene/release effects just to drums from the xpad / sampler but not the track underneith.