You can manually define a list of multiple issues to be synchronized by importing a synchronization information file to Backbone.
This is especially helpful, for example, if you want to migrate multiple issue synchronizations to Backbone after you have been using a different synchronization solution, or have been syncing manually.
Create the synchronization information file
Firstly you must create the synchronization information file. The file must be in CSV format, and must contain two columns separated by commas. The first column contains the issue keys of the first project, and the second column contains the issue keys of the second project.
When you are finished, the file should look something like this:
AG-1433,AN-527 AG-1434,AN-528 AG-1435,AN-529 AG-1436,AN-530 AG-1437,AN-531
Import the synchronization information file to Backbone
To import the synchronization information file, you first have to stop your synchronization by navigating to Project settings > Issue Synchronization > click the name of the desired synchronization in the Name column > click the three dot icon in the top-right of the screen > Stop.
Now the synchronization is stopped, click the three dot icon > Pair existing issues, and then import your CSV file using the dialog. Now you can restart your configuration.