One of Outlook's little known gems is the SQL filter in the Views Filter dialog. Although it looks confusing and technical, it's surprisingly easy to use. In many cases, you can let Outlook create a query for you by creating your criteria on the other tabs then enable SQL filtering and edit the query as needed. While you can create power filters if you know some SQL syntax, you don't need to know a lot about SQL to create filters not possible using the other filter tabs.
If you use the filter dialog often, you've already discovered the filters use the AND operator to string different criteria together. For example, you can create filters to view messages "From Amy AND Received in the last 7 days ", but not filters for messages "From Amy OR Received in the last 7 days". The filter dialog doesn't support the NOT operator directly, although you can use the Advanced filter to create some NOT filters indirectly. Using the SQL filter, you can easily create OR and NOT filters.
Switch to the SQL tab and change the AND to OR, so the rule shows all e-mail from Amy OR all e-mail that was received in the last 7 days.
You can also use the NOT operator to restrict views. This filter shows all messages not from Amy that were received before yesterday.
See Using Query Builder another option to use AND / OR operators in the filter dialog.
Am I right in understanding there's just no way to get this to show on the Advanced Find dialogue?
Correct. It's not available on all filter dialogs and there is not a registry key to add it. You can add the query builder, which gives control over AMD/OR operations.
Thanks for confirming DIane. I've added the QB already.