Go into the original rig file. You’ll have to edit each property and check “Make Library Overridable”
You can find the source for each property by hovering over the button in the UI.
I don’t have access to check out the most recent Rivet Rig but the arm_vis should still be located in the root bone’s bone properties.
https://docs.blender.org/manual/en/latest/files/data_blocks.html?highlight=library%20overridable#user-interface
