Using robot with closed loop structure in Moveit

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I might not phrase my question properly, my apologies. I know how to export from Solidworks to URDF. My issue is that Moveit only accepts tree type of structure and do not accept closed structure due to the URDF limitation. If I set the link in the image to mimic, what should I do to the upper link to make it move correctly, i.e the motion should be according to the four-bar linkage, where the upper-link motion will be close to linear motion with slight rotation.

Let's say the joints in the four bar linkage are called J_a, J_b, J_c, J_d.

J_b has the same angle as J_a, right? So set it as a mimic joint of J_a.

J_d has the same angle as J_c, right? So set it as a mimic joint of J_c. Now it's a serial manipulator as far as MoveIt knows. Or am I missing something?

I might not phrase my question properly, my apologies. I know how to export from Solidworks to URDF. My issue is that Moveit only accepts tree type of structure and do not accept closed structure due to the URDF limitation. If I set the link in the image to mimic, what should I do to the upper link to make it move correctly, i.e the motion should be according to the four-bar linkage, where the upper-link motion will be close to linear motion with slight rotation.