Vader's ability says,"after you perform an action, you may spend 1 Force to perform another action".

Could I use this multiple times? Let's say I first target lock, then spend Force to barrel roll (white), then spend Force to focus.

Yes

1 hour ago, sthej said:

Vader's ability says,"after you perform an action, you may spend 1 Force to perform another action".

Could I use this multiple times? Let's say I first target lock, then spend Force to barrel roll (white), then spend Force to focus.

At the cost of your force pool on him. Remember you only regen 1 force token per game turn, so while Vader can dump all of his tokens in one round for some extreme action stacking, he'll be lacking in the defensive or offensive mods that those tokens represent after they've been spent for the actions. The only way to fully refill Vader's force pool at the mmoment is by disengaging and not using the tokens for a few turns. It is a trade off that you'll have to weigh.

1 hour ago, sthej said:

Vader's ability says,"after you perform an action, you may spend 1 Force to perform another action".

Could I use this multiple times? Let's say I first target lock, then spend Force to barrel roll (white), then spend Force to focus.

Yes, subject to other interactions. Advanced Sensors, for example, prevent you from doing other actions. Vader can't chain off of AdvS actions (but can off of Supernatural Reflexes actions). If you Focus then link into the red Barrel Roll, you'd be stressed and couldn't do more actions.

Thanks!!