The Filters button allows you to create, rename, delete and assign filters for the selected client.

Create - allows you to create a new filter, or sub-filter for the selected client. Without any filter selected the create button will create a new top level filter, to create a sub-filter, select the appropriate filter, then select create. 

Rename - selected the appropriate filter, then Rename to change the filter name - only filters created for the selected client can be renamed - firm level filters cannot be renamed for the client, they need to be changed as a firm wide setting.

Delete - allows you to delete a filter that has been created specifically for the selected client. A warning message will appear when deleting a filter.

Assign - as the name suggests, this allows you to assign a filter, for a document that does not have a filter assigned, or to changed the assigned filter. Select the appropriate document, then select the assign option for filters and you will see this window to allow you to select the appropriate filter. By selecting one document and holding down the shift or control key you can select multiple documents to enable assigning filters in bulk.