Sadly the hotbar icons will differ between each of the "different" nukes
If I can remember correctly from my NT there's 4-5 categories of nukes:
-Short cast/Medium Recharge (around 1/3 for most of them, nice to have for a quick finisher when at low levels or for high levels if you get init debuffed)
-Medium cast/short recharge (around 3/1 for most of them and the ones that most of the time will give you the best DPM (damage per minute) and can quickly be insta-casted with enough nano init)
-Medium cast/medium recharge (around 3/3 for most of them, these often have a bit higher minimum dmg so they can be handy in the Shadowlands. They can also contain debuffs in addition, such as Crown of Frost
which debuffs nano skills)
-Long cast/medium recharge (Veeery long cast time, so mostly just an opener if you can attack something before it sees you)
-AoE (Area of Effect nanos, pewpew!)
Might've missed some of them since it's been a long time since i played my NT seriously.
What I found out was a good idea was to have each of the top one of these I could cast on a certain spot on a second hotbar, as well as having some of the ones that debuff after those.
My NT prolly has the most messy hotbar of all my chars for obvious reasons, hehe. Gotta be quite organized to play an NT effectively