At the top right corner of the client is a small quick search box. As administrators, we can configure custom searches for this box, and there is a token available called "%(SearchQuery)". Is there another token available that allows us to input the currently selected folder? For example, I could build an advanced query that uses the "Within Folder" search, and replace the folder path with the currently selected folder token.
Can a custom search be built to only search on the currently selected folder?
The search query token is the only token available for the Custom Search Box. There are however other ways to accomplish a current folder search. A few options include creating a saved search in the Search Pane in Client, creating a toolbar button in Client to perform the search or using Workflow. Your specific case will determine the best option for you.