Yours looks different, mine is (was) soft rubber. It was cast in place and I had to saw it off with a hacksaw. That was to replace it with a third function knob.
Have you tried removing the whole lever, though, and replacing the boot from the bottom?
Mine are like yours... Twist, pull and cuss a lot.I have taken mine off on a Kubota L3010 but yours is probably different. It was a while back but I remember twisting it first with a lot of force then when it moved I had to push it off twisting because pulling just tightened it. Mine is hard rubber not molded plastic.
gg