The Link Filter parameter mentioned in Link Scheme definition is currently used for filtering the issue proposed for a potential link action.
But the filter is not used as is.
If your initial filter is by example :

project = "TSTB" AND status not in (Closed)

When used in CreateAndLink screen for an Issue TSTA-1 of Test A (TSTA), the Query is extended with extra criteria (initially there were the only criteria used) :

• to specify the Issue Type defined in Link Scheme :

  issuetype = "<OutwardLinkId>"

• to avoid recursive link :

  key != "TSTA-1"

• to limit the list to issues in same project :

  project = "TSTA"

• to limit the list to issues having the Source Summary mentioned in their Summary, Environment or Description :

  summary ~ "Test" OR description ~ "Test" OR environment ~ "Test"

We have then the below query :

project = "TSTB" AND status not in (Closed) AND project = "TSTA" AND issuetype = "1" AND NOT key in ("TSTA-1") AND ( summary ~ "Test" OR description ~ "Test" OR environment ~ "Test" )

Now, we will 2 cases :

• Without select filter :

  project = "TSTA" AND issuetype = "1" AND NOT key in ("TSTA-1") AND ( summary ~ "Test" OR description ~ "Test" OR environment ~ "Test" )

• With select filter :

  project = "TSTB" AND status not in (Closed) AND NOT key in ("TSTA-1")