_concat

Concatenates the Lists given as parameters -- Function
_concat (lists) -> The same Type
lists
One or more lists
Produces
All of the given lists, concatenated together
Occasionally, you want to take several separate lists, and treat them as a single list. This allows you to do something like
[[My Thing -> _concat(Primary Sources, Secondary Sources) -> _bulleted]]
Note that the received context will be passed to each of the expressions in lists, as usual, but otherwise isn't relevant. You can write expressions that completely ignore the received context.
You can _concat lists that are of different but compatible Types. If you do this, the resulting list will all be coerced to the first Type found.