I've owned 3 Deere's (3033r, 855, 750), and all had two different positions for the pins on the connectors between the rockshaft arms and lower link arms, one of which allowed the lower links to float or lift independently.
On the 3033r, you just turn the lower link pins a quarter turn.
Floating:
View attachment 3712603
Fixed:
View attachment 3712604
Note the keyway slot type pin head is turned from vertical to horizontal. It's right there in the manual of every tractor I've ever owned, although the exact hardware used is slightly different on each.
Is this something only Deere does? I can't imagine having a tractor without this simple feature.