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Possible onset of the quantum plasticity in soft–solid He-4 was discovered recently in 7 nm diameter (Vycor glass) nanopores. Here, by using the transition-state model together with the specific activation energy and activation volume, we investigated the possible frictionless plastic flows of soft–solid He-4 under high pressure in confined nanodomains and we observed a series of sudden changes in the shearing stresses at corresponding very high shear strain rates of (locally amorphous) soft–solid He-4 for different activation volumes considering the role of He-3 impurities. Our calculated critical velocity for a fixed concentration of He-3 quantitatively agrees with recent reported values.