proper tagging and sorting criteria? do it once, do it right.
If you mean move inactive nodes to "Lost & Found" then you can use a server task that is tied to a query. Such as, look under "Server Taks" for "Inactive Agent Cleanup Task" which is tied to query "Managed Incative Agents" (Lists all managed systems whose agents have not communicated within the last month.).
Edit "Inactive Agent Cleanup Task" and under "Sub-Actions" pick "Move Systems to another Group" and to the right of "System Tree group" choose Lost and Found
There might be an easier way but this works.