What version of MODX?
And what do you know about the page you want to get the ID of (pagetitle, resource group membership, ??) ?
Also, if you can say why you want the ID, there might be another way to do what you want.
[[!Login?loginResourceId=`[[*MemberPageID]]`]]
How about putting the ID of the new page in a Template Variable called MemberPageID attached to that template? Then your snippet property would look like this:
[[!Login?loginResourceId=`[[*MemberPageID]]`]]
When a new issue comes out, you’d just edit the login page and enter the new ID in the TV.
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