You could slave chain a group ships together, so just that group attacks a target and a different group attacks a different target. (That was for example). For more info: [http://starwars.wikia.com/wiki/Katana_fleet] this should help.
Spam R+F? If your fleet is large enough for this to make sense then it is also large enough to steamroll more or less anything you come across.
I was going to open a new issue but OP is pretty close to what I was thinking too. Basically, I would like to be able to establish groups or "fleets" inside my collection of unparked ships and give different instructions to each group. For instance, before getting access to Flycatchers, I would use 20 Blackbirds with anti-missile turrets and the problem I have is that I want to tell my Blackbirds to stay near my Dreadnoughts while they attack from afar with projectiles.
@quantumandan
You can instruct a ship to follow another ship. So it is possible to ask a blackbird to follow a dreadnought, and use a command group to select the dreadnoughts and issue attack orders that only they will follow.
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Spam R+F? If your fleet is large enough for this to make sense then it is also large enough to steamroll more or less anything you come across.