如何为自定义角色提供仅编辑SPECIFIC菜单的功能

I am trying to make a Wordpress site with custom roles and custom capabilities. I have already wrote my own PHP plugin that can create these custom roles, but now I am faced with a capability problem. I would like to have a custom user role that can edit the Menu items under the Appearance tab. But I don't want my custom role to have the ability to edit every menu on my WordPress site. I only want this role to be able to edit a single menu. For example, in the screenshot below, I want the user role to only be able to access Menu A. I don't want the role to have access to Header, Footer, or any other menus.

I have searched other Stackoverflow questions like this one: https://wordpress.stackexchange.com/questions/4191/allow-editors-to-edit-menus

But that solution allows the role to access every menu on my Wordpress site. In fact, that solution allows the role to access other Appearance functionalities like the ability to customize the theme itself, which I don't want.

I think the solution to my problem is that I need to add a filter onto the list of Menus that shows up in the dropdown(the one that contains Header Menu, Footer Menu, and Menu A in my screenshot). Ideally this filter would only show "Menu A" to my custom role. But I am not sure where to start, so any help would be much appreciated.