I believe that this comment is correct:
 

Isn't it what can be achieved by using the "filter" keyword ?
if you define a filter which is: filter = "My Filter1" or filter = "My Filter2", you get the joined result of the two filters.

I believe this ticket should be closed, but I will wait a week before taking any action in case anyone disagrees. Thank you!

Our devs mostly use a single kanban board (I'm sick of managing multiple boards and creating new quick filters every week) which lets them filter by project, and fixVersion. They pick those 2 quick filters and they see the tickets for the feature release they've been assigned to.

This works beautifully, and has made things more consistent all the way around for our 25+ dev team.

Filter Query:

project in ("Slickdeals iOS App", "Slickdeals Android App", Slickdeals) ORDER BY Rank ASC

Kanban board sub-filter:

fixVersion in unreleasedVersions() OR fixVersion is EMPTY

Quickfilter:

fixVersion = "Coupons 3.0"

My new use case is that there may be an Epic in that fixVersion, and I want to see all of the Epic's children on the board as well. To support this I need the ability to have the board's "Filter Query" + "Kanban board sub-filter" + All quickfilters = (THIS.JQL). Then inside the Quickfilter itself I could use (THIS.JQL).

NEW Quickfilter:

fixVersion = "Coupons 3.0" OR issueFunction in linkedIssuesOf( (THIS.JQL), "is Epic of")

The above filter would let me create new quickfilters for each fixVersion, and support breaking out all matching Epic's children. This would be the only way to make the flexible board I've created support this use case. The comparable JQL for this would be:

project in ("Slickdeals iOS App", "Slickdeals Android App", Slickdeals) AND (fixVersion in unreleasedVersions() OR fixVersion is EMPTY) and fixVersion = 'Coupons 3.0' and project = ANDAPP OR issueFunction in linkedIssuesOf("project in (\"Slickdeals iOS App\", \"Slickdeals Android App\", Slickdeals) AND (fixVersion in unreleasedVersions() OR fixVersion is EMPTY) and fixVersion = 'Coupons 3.0' and project = ANDAPP", "is Epic of") ORDER BY Rank ASC

SQL for JIRA transforms JQL into standard SQL therefore you could use the standard SQL JOIN operator to perform the join of two (or more) JQL functions and use the built in sql JQL function to transform the SQL into a JQL again:

issue in sql("
select i1.key from issues i1
inner join issues i2 on i1.id=i2.id
where
i1.jql='<JQL1>'
and
i2.jql='<JQL2>'
")

Isn't it what can be achieved by using the "filter" keyword ?
if you define a filter which is: filter = "My Filter1" or filter = "My Filter2", you get the joined result of the two filters.

Would be a very nice feature !

@ Fiona - does not look this will be done anytime soon, the parent ticket was created back in 2010 and hasn't been prioritized yet. This sub-task is one of 29 open ones......

Our company would really need this to create a perfect dashboard.

Is this likely to be done in the near future

Adding my vote to this. We are rolling JIRA out to our Enterprise and this is a request we get most often from our Support teams.