Use PhpPgMyAdmin to detect your docker postgres instances

config.inc.php

<?php
# phppgmyadmin/conf/config.inc.php

(...)
  // Docker postgres connections
  $server_i = 1;
  $containers = explode("\n", trim(`docker ps`));
  array_shift($containers);
  foreach ($containers as $cid) {
    if (!preg_match('/postgres/', $cid)) { continue; }
    $cid = substr($cid, 0, 12);

    $container = json_decode(`docker inspect {$cid}`);
    if ($container) {
      $container = $container[0];
      $port = array_keys((Array)$container->NetworkSettings->Ports)[0];
      $port = +explode('/', $port, 2)[0];

      $conf['servers'][$server_i]['desc'] = substr($container->Name, 1);
      $conf['servers'][$server_i]['host'] = $container->NetworkSettings->IPAddress;
      $conf['servers'][$server_i]['port'] = $port;
      $conf['servers'][$server_i]['sslmode'] = 'allow';
      $conf['servers'][$server_i]['defaultdb'] = 'template1';
      $conf['servers'][$server_i]['pg_dump_path'] = '/usr/bin/pg_dump';
      $conf['servers'][$server_i]['pg_dumpall_path'] = '/usr/bin/pg_dumpall';
      $server_i++;
    }
  }

Assumes your containers are running and have 'postgres' in their image name or container name.