WordPress Create Custom Capability

You should first understand that Wordpress user roles are simple as set of capabilities. That being said, since you said you are creating a plugin, I like to think you are no stranger to code and hence not afraid to code your solution rather than using another plugin for this.

This code should help you create a new user role and add custom capability to it.

<?php// create a new user rolefunction wpeagles_example_role(){    add_role(        'example_role',        'example Role',        [            // list of capabilities for this role            'read'         => true,            'edit_posts'   => true,            'upload_files' => true,        ]    );}// add the example_roleadd_action('init', 'wpeagles_example_role');

To add a custom capability to this user role use the code below:

//adding custom capability<?phpfunction wpeagles_example_role_caps(){    // gets the example_role role object    $role = get_role('example_role');    // add a custom capability     // you can remove the 'edit_others-post' and add something else (your     own custom capability) which you can use in your code login along with the current_user_can( $capability ) hook.    $role->add_cap('edit_others_posts', true);}// add example_role capabilities, priority must be after the initial role     definitionadd_action('init', 'wpeagles_example_role_caps', 11);

Futher reference: https://developer.wordpress.org/plugins/users/roles-and-capabilities/

You can create custom roles and capabilities by plugin. Two options available there by custom code or you can use existing plugin.

For Custom code:https://wordpress.stackexchange.com/questions/35165/how-do-i-create-a-custom-role-capability

Using existing plugin: User Roles and Capabilities