I may target an enemy at a connecting location with this combo ?

I believe the answer is "no" because Flamethrower states that "the enemy chosen for this attack must be the enemy engaged with you with the highest Fight" - Marksmanship says "you can target an enemy at an adjacent location", but all that does is increase the range of possible targets (i.e. normally you can only target enemies at your own location, now your range of possible targets includes enemies at your location and adjacent locations), whereas "Must" means that of all the available options, you must choose the one that is "the enemy engaged with you with the highest fight" - Marksmanship doesn't include the word "instead" so it isn't a replacement effect, it just expands the normal range of options, whereas Flamethrower takes away your ability to choose from the range of options available.

Even if you could, it wouldn't really matter much (except for making the shot easier) because you could only assign damage to enemies engaged with you, regardless of where your target is (the damage assignment of Flamethrower is a replacement effect so it overrides the normal damage assignment).

Edit: The only benefit of using Marksmanship with Flamethrower is that you can ignore the Retaliate keyword.

37 minutes ago, Allonym said:

I believe the answer is "no" because Flamethrower states that "the enemy chosen for this attack must be the enemy engaged with you with the highest Fight" - Marksmanship says "you can target an enemy at an adjacent location", but all that does is increase the range of possible targets (i.e. normally you can only target enemies at your own location, now your range of possible targets includes enemies at your location and adjacent locations), whereas "Must" means that of all the available options, you must choose the one that is "the enemy engaged with you with the highest fight" - Marksmanship doesn't include the word "instead" so it isn't a replacement effect, it just expands the normal range of options, whereas Flamethrower takes away your ability to choose from the range of options available.

Even if you could, it wouldn't really matter much (except for making the shot easier) because you could only assign damage to enemies engaged with you, regardless of where your target is (the damage assignment of Flamethrower is a replacement effect so it overrides the normal damage assignment).

Edit: The only benefit of using Marksmanship with Flamethrower is that you can ignore the Retaliate keyword.

Agreed.

I like that it takes up a Body & Two-Hand slots. Have we seen any cards that have multiple slot icons before?

11 minutes ago, Duciris said:

I like that it takes up a Body & Two-Hand slots. Have we seen any cards that have multiple slot icons before?

I don't think so. I wonder if the guardian/mystic dual class card seen in The Secret Name preview article will take 1 Hand + 1 Arcane?