When synchronizing issues of two projects, you can configure which issue types Backbone Issue Sync should synchronize for you. However, you might not want to synchronize all of the issues which share the same issue type, but only a small subset of them. Therefore Backbone offers an option to enter a filter based on the Jira Query Language (JQL). For example, you can filter your issues based on status, a label, creation date, and so on. This filter will be evaluated before synchronizing any issue (and also any issue change) between your projects. You can find the option under Configuration > Issue Types > Limit Issues.
A JQL can be entered for both sides of your synchronization. Hence, you can limit the issues for the direction Project A → Project B by providing a JQL on the side of Project A (and vice versa). The JQL you are entering will always be scoped to the project where it is applied to.
Verify Your JQL
You can verify that your JQL works as expected by clicking on the Magnifier icon. This will trigger a mechanism in Backbone which validates the JQL. If your JQL is correct, you'll see how many issues are matched by your JQL for the specific project. If your JQL is not correct, you'll see that an error appears. You can then click on Run in Jira search to test this JQL using the regular search feature in your Jira system. If you're done and everything works as expected, you can Save your JQLs.
Note About User Data
Atlassian has announced the deprecation of usernames and user keys for Jira Cloud - you can read our article with more information about this topic. This will prevent you from using a JQL filter with a username like "assignee = admin" if the related project is on a Jira Cloud instance. If you use the Verify button, we'll make sure to replace these occurrences of usernames and user keys and replace your JQL with an updated JQL. The updated JQL is using Account IDs instead of usernames. Please make sure to check the JQL again afterwards, i.e. if it's still correct. If you encounter any problems here, please reach out to us using our support system or write an email to firstname.lastname@example.org.