As the iRite link window allows for a browse the server option as shown in the first screen shot on this page:
Links%2C_E-Mails_and_Anchors
I’d assume that you can set the location that you can browse within. The options for the file type resource on this page:
Built-in
Indicates that you can set the directory. I’m not sure if you can have the browse enabled, but not allow uploads in case that comes up.