You can add additional arrows in the edit mode (3rd picture in OP).
I think that is only for adjusting the axis of attack (advance arrow) and the ends of your Front line I could be wrong but as far as I can tell...
From left to right.
1\ Naval invasion.
2\ Airborne invasion\drop.
3\ Missing function.
4\ Border Front line and Defensive Front line both are similar and both do not require an advance arrow. (axis of attack)
5\ Draw Offensive Front line.
6\ Edit Tool for adjusting the axis of attack ( advance arrow) and for connecting to other Front lines (phases ) and toggle to adjust ends of Offensive Front lines. I would guess that as you adjust your Offensive Front Line its axis adjusts accordingly but you can also fine tune the axis yourself.
7\ Tool for adding Troops to Front lines I presume you can toggle to add or subtract troops.
Basically everything we knew and saw already in the vids.
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