Allow group administrators and moderators to manage group-associated BuddyPress Docs.

bp_docs_groups_allow_group_admins_to_manage_access.php

<?php
add_filter( 'bp_docs_map_meta_caps', 'bp_docs_groups_allow_group_admins_to_manage_access', 20, 4 );
function bp_docs_groups_allow_group_admins_to_manage_access( $caps, $cap, $user_id, $args ) {
	// We only want to act on the "manage" capability, in group situations.
	if ( 'bp_docs_manage' !== $cap ) {
		return $caps;
	}
	$doc = bp_docs_get_doc_for_caps( $args );
	if ( empty( $doc ) ) {
		return $caps;
	}

	$group_id = bp_docs_get_associated_group_id( $doc->ID, $doc );

	// If not associated with a group, nothing to do here
	if ( ! $group_id ) {
		return $caps;
	}

	if ( groups_is_user_admin( $user_id, $group_id ) || groups_is_user_mod( $user_id, $group_id ) ) {
		$caps = array( 'exist' );
	}

	return $caps;
}