Quite often when moving fleets around hostile gravity wells, they will stray near a valid target and engage them in a pitched battle.
However, I would like a fleet to avoid a battle unless specifically told otherwise. The 'Fleet stance' toggle button does not seem to have the intended effect- setting it to 'Evasive' causes an FTL jump to be triggered if a hostile fleet is present in the same system; however targets are still engaged with wild abandon.
My intent is to try and get a fleet caught behind enemy lines home safely. It has a small head start on the much larger doomstack pursuing fleet:
But since it is retreating through enemy systems, it will likely get caught up on a station near the FTL exit point, whereupon the pursuing fleet will be able to catch it and do significant damage even before the emergency FTL spools up.
How can I get this fleet home safely, without it stopping to engage a pitiful-but-obviously-very-strategically-important research station along the way?
This has a clear second type of use as well: if an interdiction fleet - say one that has a battleship with an FTL inhibitor - wants to hold an enemy fleet in a system for destruction, it would be handy if you could give the fleet a clear order1 to engage that fleet first and foremost, and not the mining station that happens to be in between the two fleets.
1: I know fleets in Stellaris are supposed to have a fairly large degree of autonomy, for example in regards to battle engagement doctrine, so this behaviour may be intended.
It's just unfortunate that the autonomy they have means engaging pointless targets, or equally comically the thinking that goes "Hey, my fleet is equipped with long range armaments and theirs is short. RAAAGH LET'S CHARGE TO RAMMING DISTANCE!"