Add in other dynamic/indirect tokens.

config/install/dgi_members.settings.yml

@@ -1,2 +1,5 @@
+---
 allow_compound_display_for_non_compound: FALSE
 display_non_compound_compound_as_first_member_of_itself: FALSE
+member_parameters:
+  - active_member

config/schema/dgi_members.schema.yml

@@ -1,3 +1,4 @@
+---
 dgi_members.settings:
   type: config_object
   label: 'DGI Members Settings'
@@ -8,3 +9,9 @@ dgi_members.settings:
     display_non_compound_compound_as_first_member_of_itself:
       type: boolean
       label: 'Display compound non-Compound Object as first member of its set.'
+    member_parameters:
+      type: sequence
+      label: 'The URL query parameters for which we will attempt to manage "active member" tokens.'
+      sequence:
+        type: string
+        label: "A URL query parameter of interest."

dgi_members.post_update.php

@@ -0,0 +1,17 @@
+<?php
+
+/**
+ * @file
+ * Post-update hooks.
+ */
+
+/**
+ * Implements hook_post_update_NAME().
+ */
+function dgi_members_post_update_add_params(&$sandbox) {
+  $config = \Drupal::configFactory()->getEditable('dgi_members.settings');
+  $config->set('member_parameters', [
+    'active_member',
+  ]);
+  $config->save(TRUE);
+}

dgi_members.tokens.inc

@@ -0,0 +1,75 @@
+<?php
+
+/**
+ * @file
+ * Token hooks.
+ */
+
+use Drupal\Core\Render\BubbleableMetadata;
+
+/**
+ * Implements hook_token_info().
+ */
+function dgi_members_token_info() {
+  $config = \Drupal::config('dgi_members.settings');
+
+  $parameter_tokens = [];
+  foreach ($config->get('member_parameters') as $parameter) {
+    $parameter_tokens[_dgi_members_get_token_name($parameter)] = [
+      'name' => t('Active member from @parameter (dgi_members/Compound)', [
+        '@parameter' => $parameter,
+      ]),
+      'type' => 'node',
+    ];
+  }
+
+  return [
+    'tokens' => [
+      'node' => $parameter_tokens,
+    ],
+  ];
+}
+
+/**
+ * Implements hook_tokens().
+ */
+function dgi_members_tokens($type, $tokens, array $data, array $options, BubbleableMetadata $bubbleable_metadata) {
+  if ($type != 'node') {
+    return;
+  }
+
+  $output = [];
+
+  $config = \Drupal::config('dgi_members.settings');
+  /** @var \Drupal\dgi_members\DgiMembersEntityOperationsInterface $member_service */
+  $member_service = \Drupal::service('dgi_members.entity_service');
+  foreach ($config->get('member_parameters') as $parameter) {
+    $mapped = _dgi_members_get_token_name($parameter);
+    $prefix = "{$mapped}:";
+    $to_chain = [];
+    foreach ($tokens as $key => $value) {
+      if (str_starts_with($key, $prefix)) {
+        $to_chain[substr($key, strlen($prefix))] = $value;
+      }
+    }
+
+    if ($to_chain) {
+      $bubbleable_metadata->addCacheContexts([
+        "url.query_args:{$parameter}",
+      ]);
+      $output += \Drupal::token()->generate(
+        $type,
+        $to_chain,
+        ['node' => $member_service->retrieveActiveMember($parameter)] + $data,
+        $options,
+        $bubbleable_metadata,
+      );
+    }
+  }
+
+  return $output;
+}
+
+function _dgi_members_get_token_name($parameter) {
+  return "dgi_member__{$parameter}";
+}