If you quickly mount and dismount a strider the strider then go onto a differnt strider. will float/fly.After further testing this seems to completely remove their gravity allowing you to lift them up even higher using a fishing rod or lead. nothing seems to cancel this state including damage, or riding it, or putting it back in the lava. putting it through the portal works but will nearly immediately despawn. The method is not consistent but i have gotten it 6 times on different striders and seems to require you flying in creative mode.