Like from the episode "Now We're Only Falling Apart" before Pink Diamond fake her own shattering, Pink can shapeshift to become a disguise of Rose Quartz and back to herself, Steven called Lion and before go to the junkyard in the Desert, Pearl showed Yellow and Blue Diamond that Pink can shapeshift to become Rose Quartz and back before fake her shattering. Blue and Yellow were surprised. Then Blue Diamond goes first and shapeshift smaller, then Yellow shapeshift next. After that, Garnet, Amethyst, Pearl and Bismuth hop on Lion's back, Steven and Connie hop on Lion's mane then he said, "Hop aboard Yellow and Blue." so he grabbed Blue's hand to get in the mane and grabbed Yellow's hand in the mane. Steven said to Yellow and Blue Diamond "Hang on." then Lion roar through the portal and Yellow and Blue Diamond had a first time through Lion's portal. They arrived at Rose's Landfill in the Desert. Steven, Connie Yellow and Blue Diamond get out of Lion's mane and Garnet, Amethyst, Pearl, and Bismuth hop off the back, and Yellow and Blue Diamond shapeshift back themselves.
Nice, but I doubt the Diamonds would need to be told they can shapeshift because Pink could. They may be a bit uncomfortable making themselves smaller in front of "lesser" Gems, but they would still know how to do it.