6) Mothballing fleets - Always
7) Army template - Always
8) Province siege objective for allies - Often
Where do I find these 3 lol? I got Art of War but just started playing.
Mothballing fleets is the bottom-left button (or thereabouts) that looks like an anchor, on the interface when you have a navy selected (same place where you set them to trade/pirate/patrol).
Army template comes from the build interface (press B or use the button in the top-left near your nation's shield). Get to the 'units' tab, you'll see your military units, then mercenaries, then 'Create Template'.
Siege objectives for allies are, I think, on the province view.
For myself:
1) Selling ships to someone - Never
2) Creating a client state - Not yet, but seems interesting for late-game (I've played a few campaigns to the 17th c and moved to another)
3) Setting a vassal's war assistance mode - I've used it, but it seems pretty wonky to me so I generally let them do their own thing.
4) DoW in support for rebels - Not yet, but looks really valuable in some situations.
5) Sortie from sieges - Never
6) Mothballing fleets - I do use this, it's a nice feature. Early colonialism often just needs a few transports to move troops around, no need to pay for the big navy.
7) Army template - Yes, it's nice. I'm currently using a 5/1/4 setup, then combine to suit (i.e. two armies makes a 10/2/8, a nice fighting stack, using 3 or 4 when necessary)
8) Province siege objective for allies - Haven't really tried it yet, sounds useful though.
9) Swapping occupation - Happy to see allies and vassals swapping to me, but otherwise no.
10) Designating as marches - Not yet, but I have some ideas of where I would use it.