No you don't need <%ID%>

You need:

<input type="hidden" name="Current URL" value="<%URL%>">

If the Current URL field is empty you'll get the error you experienced.

Snippet from modify.cgi:

# Make sure we have a link to modify.
!$in{'Current URL'} and &site_html_modify_failure ("You did not specify link to modify") and return;