The function `prepend_prevdepth` is available in both namespaces, both node.* and node.direct.*.

node.*: https://gitlab.lisn.upsaclay.fr/texlive/luatex/-/blob/master/source/texk/web2c/luatexdir/lua/lnodelib.c#L9132
node.direct.*: https://gitlab.lisn.upsaclay.fr/texlive/luatex/-/blob/master/source/texk/web2c/luatexdir/lua/lnodelib.c#L9030

diff --git a/manual/luatex-nodes.tex b/manual/luatex-nodes.tex
index 9b72fdf2c..347987d41 100644
--- a/manual/luatex-nodes.tex
+++ b/manual/luatex-nodes.tex
@@ -2391,7 +2391,7 @@ consistency. You can of course always define additional accessors using \type
 \supported {mlist_to_hlist}          \yes \nop
 \supported {new}                     \yes \yes
 \supported {next}                    \yes \nop
-\supported {prepend_prevdepth}       \nop \yes
+\supported {prepend_prevdepth}       \yes \yes
 \supported {prev}                    \yes \nop
 \supported {protect_glyphs}          \yes \yes
 \supported {protect_glyph}           \yes \yes