Brendan Anderson
--- a/src/Form/MigrationExecuteForm.php
+++ b/src/Form/MigrationExecuteForm.php
      '#description' => $this->t('Check this box to update all previously-imported content in addition to importing new content. Leave unchecked to only import new content'),
    ];

+    $form['options']['sync'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Sync'),
+      '#description' => $this->t('Check this box to sync source and destination. Delete destination records that do not exist in the source.'),
--- a/src/Form/MigrationExecuteForm.php
+++ b/src/Form/MigrationExecuteForm.php
    $options = [
      'limit' => $form_state->getValue('limit') ?: 0,
      'update' => $form_state->getValue('update') ?: 0,
+      'sync' => (bool)$form_state->getValue('update'),