Real life demo, DK have some default buffs to track:
Death Trance - buff detected and warned about, Horn of Winter - warned to cast it, Rune Strike - reactive spell availability detected.
UI settings for 'effects', which can be permanent or activated upon some rules.
One of my characters with some useful notifications set in action
main options page.
The general UI settings for the notification: colors, fonts, sizes etc.
The rules, i.e. checks to perform for effects to be activated,
Logic rules to check for every spell in list for this notification.
This is how you'll see (bu default) the trackable buffs (on right from player) and reactive spells (on left from player).
For the screenshot, I took the (always) available spells - just to make them visible for a moment. Unfortunately, I don't...
When no defined spells can reach the target, main distance window will be with "out of range" settings.
distance spell list
Help page for an addon with some basic explanation on what to do and how.
Choosing the spells for one notification, you can make a list of them.
Some spell can reach the target and being visualized as defined in options.
Rules to check to activate the notification. This logic applies before all spells in least checked separately.
You can turn "demo" to see where are your notifications places to adjust their settings and see changes on display at the same time.