These WeakAuras track buffs and available cooldowns, and provide an APL for combo point builders and finishers. This explicitly does not show actions when they're on cooldown, as I personally find it noisy, and use OmniCC instead.

These explicitly show when usable. Without an attackable target, they hide.

This is a collection of 18 auras:

Right side:

Nightblade Off (blinks when usable and target doesn't have debuff)

Nightblade Debuff (desaturated with countdown)

Nightblade Pandemic (saturated and pulsing with countdown)

Dance Buff (saturated with countdown)

Dance Charges (desaturated with number of stacks)

Symbols Buff (shows countdown)

Symbols high energy (desaturated if you'd energy cap)

Symbols low energy (saturated if safely usable)

The APL:

Builders (shown with <5 combo points, does not check NB because it might not be primary target):

Shadowstrike (when usable)

Backstab (when SS not usable; automatically switches to Gloomblade)

Goremaw (shows when not in stealth and <= 85 energy, as the regen is over 6 seconds)

Finishers (shown with >= 5 combo points, excludes NB as it's to the right):

DFA with SoD (saturated, checks SoD is up with >1 left)

DFA w/o SoD (desaturated, when SoD is not yet up)

Eviscerate (when DFA is not usable)

Center:

Vanish Up (when usable)

Empty spot in the grid here to fill in with whatever (arcane torrent, trinket, etc.)

Left side:

Kick (shows when target is interruptible and usable)

Blades Buff (desaturated with countdown)

Blades Up (saturated when usable)

Mantle Buff (I used this more when playing assassination, it's less relevant now, might remove)

I also highly recommend these two macros to avoid wasting Shadow Dance and Vanish:

Shadow Dance Macro:

showtooltip Shadow Dance

/cast [nostance] Shadow Dance

Vanish Macro:

showtooltip Vanish

/cast [nostance] Vanish

/cast Shadowstrike

/stopattack