Using a data explorer query to generate a list of tags, and searching for those with hyphens, I found that Islam.SE has the following compound tags:
halal-haram (715 Q's) is a compound of halal and haram. Meta threads: 1. How should we tidy up the halal/haram family of tags? 2. When to use haram and halal-haram tags?
shia-sunni (69 Q's) is a compound of shiism and sunni. Meta thread: What is the "shia-sunni" tag for? Do we even need it?
(I might have missed some in Arabic.)
This post is a question:
Compound tags: Do we need them?
What I think:
The compound tags husband-wife and men-women indicate interactions between husband and wife, and between men and women. These might therefore be better renamed spouse-interaction and gender-interaction.
It looks like it's impractically confusing to do anything but tag anything about "halal" and/or "haram" with halal-haram.
The words "halal" and "haram" are antonyms (or close enough) that any question about "halal" will automatically be about "haram". (There's a small number of exceptions I've seen of the form "Is X or Y more haram?")
"halal" also relates to "halal certification" of foods, which adds even more confusion.
shia-sunni seems to be used to ask about differences between Shia Islam and Sunni Islam. For example:
In these cases, I'd say it should be broken into its components. The word "differences" should be in the title anyway.
There are also questions about Shia-Sunni interactions, e.g.:
But it seems to get misused in several ways:
For example, the OP already knows about Sunni Islam, and asks if the same thing is true in Shia Islam. E.g. What does the word "Shia" mean?
The OP asks about Islamic sects in general. E.g. Isn't it possible for Muslim Ummah to unite under one identity?
The OP seems to like tags starting with "Shia". E.g. Can I create, own & run a Dating website?
Perhaps it could be renamed sect-interaction, like the above.
I've got no idea what sunnah-hadith is about.