If I'm understanding you, you should be able to accomplish what you want without any Resource Groups.
Create three new Policies based on the Administrator Policy Template.
Editors: uncheck element_tree and access_permissions
Writers: uncheck element_tree, file_tree, and any other things you don't want them to do (access_permissions, etc.)
Contributors: element_tree, file_tree, access_permissions, and all the document permissions you don't want them to have (publish_document, delete_document, duplicate_document, etc.).
In Security -> Access Controls -> User Group tab -- right-click on each user group and, on the Context Access tab, add an ACL entry with a context of 'mgr', a minimum role that the users have, and the appropriate policy.
On the Security menu, flush permissions and flush all sessions before testing. It's a good idea to test from another browser where you're not logged in to the Manager.
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PLEASE, PLEASE specify the version of MODX you are using.
MODX info for everyone:
http://bobsguides.com/modx.html
[ed. note: BobRay last edited this post 13 years, 11 months ago.]