The Title Block Setup dialog box lets you configure how title blocks are used. There's a special for Flex title blocks.
Title Block Folder
Specify where the title blocks are stored.
Available Title Blocks
This lists the available title blocks by filename.
Open
Click this to open the selected title block.
Disable
Click this to disable the selected title block. It won't show up in the PF tab.
Enable
Click this to enable the selected title block. It will show up in the PF tab.
(I don't think we need anything else in this dialog box now)