What permissions does a role need for the user to be assigned as the author of a post?

You probably need to add 3 capabilities: edit_published_posts publish_posts delete_published_posts but at the very least, you need to add publish_posts as that is the capability WordPress uses to determine what users are shown in Authors drop-down. Note: Changing capabilities is stored in the database so the recommendation is to modify these values via a plugin … Read more

Allowing custom role user to edit post assigned to them but don’t let them create new custom type post

You cannot find the capability because it does not exist. In WP out of the box, the paradigm is not post creation, but post publishing. Users can be adjusted to edit and create drafts and pending posts, but not publish. Setting users to only edit however is not possible at the roles and capabilities level, … Read more

grant multiple roles access to specific admin menu item

You shouldn’t use Roles to handle permissions for your menu page. Instead, use capabilities, and then assign those capabilities to whichever roles should have access. For example, instead of creating a customrole role, use a custom capability like manage_custom_plugin: add_menu_page( ‘Custom-Plugin’, ‘Custom-Plugin’, ‘manage_custom_plugin’, ‘custom-plugin’, ‘init_custom_menu_page’ ); Now, using the Members plugin you can enter manage_custom_plugin … Read more

Allow members to create groups on my site

You can use BuddyPress to create groups, manage groups, allow users to join groups and search them. BuddyPress is like a Social Network plugin for WordPress. Has it’s own sub-section/ecosystem of plugins and add-ons and code snippets that you can apply. https://en-ca.wordpress.org/plugins/buddypress/ There’s an active developer community and lots of documentation too: https://codex.buddypress.org