My main service panel is QO30M200 and the ground/neutral bars are filled.
You can see the previous owner/electrician installed two or even three wires under some of the ground bar screws which I'm not sure is allowed.
I'm adding a sub-panel and the neutral lug requires 3 spaces on the ground bar.
Here is the picture:

The right-side of the panel looks to have two ground bars. (one of them is slightly beneath the other)
Can I add a similar second ground bar to the left side? If so, does anybody know what part number I need?
Thanks again so much and I apologize for asking so many questions.
You can see the previous owner/electrician installed two or even three wires under some of the ground bar screws which I'm not sure is allowed.
I'm adding a sub-panel and the neutral lug requires 3 spaces on the ground bar.
Here is the picture:

The right-side of the panel looks to have two ground bars. (one of them is slightly beneath the other)
Can I add a similar second ground bar to the left side? If so, does anybody know what part number I need?
Thanks again so much and I apologize for asking so many questions.