The iReal Pro editor currently supports maximum 12 systems. New songs can be based on optional barline templates (up to 96 measures.*)
You can make measures half as wide fitting 8 (or more) of them per line (see adjusting bar size.)
As an example, see the "Bossa 3" exercise included with iReal Pro or "Chega de Saudade" included in the Jazz 1350 playlist.
Here is one way to reduce the spacing in a bar:
* To maximise space, where only a single chord occupies a measure, that measure could minimally be only one space (place a barline on either side of the space, with the chord inside that space). Using the small font size for that chord would be best.