I have just learned about the new function Splice
from this answer. It turns out that this function used to have a completely different usage! (See below.)
To me, this seems dangerous, to deprecate a symbol and then two versions later introduce completely different functionality to that symbol. What other symbols in Mathematica have been deprecated and then used as the name for a new function?
From my copy of Version 11.3:
WolframLanguageData["Splice"]["Timeline"]
seems incomplete. $\endgroup$