Manage Wiki Link Syntax
'Expose' means to tell trac it is used as wiki link. If you want to expose, containing separator character is not good because trac could not find as namespace (without patch).
'Display' is a optional display text of link anchor. 'URL' is target location for this link. 'Display' and 'URL' can be contain one '%s' to replace with an argument. If 'Display' is omitted, "name" or "name:arg" is used.