When you say multiple JIRA I assume you mean multiple JIRA projects. Accessing multiple projects via a classic (chart) board is not possible, this was one of the main reasons Rapid Boards were added.
You can do what you ask using a Rapid Board in v 5.8.7: https://confluence.atlassian.com/display/GH058/Using+the+Rapid+Board
The JQL behind the filter can be used to reference multiple projects, e.g.
Project in (PRJ1, PRJ2, PRJ3)
Does that work for you?
...It's true that there are projects in Jira; but they are merely a way to cut off issues, to tell them apart from other sections of work and to apply rules that are specific to that team (the schemes)....
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