Yes, that's the issue. The Dialogue System Extras page has a patch. Up to Unity version 2022.3.0, Unity misspelled the resource ("Seach"), so that's what editor code had to use. In 2022.3.1, they changed the name of the resource ("Search"), so assets had to update their editor code. The patch uses conditional compilation to specify the correct resource name (Seach or Search) depending on the Unity version.