The correlative ᴹQ. indon “as” appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of the relative pronoun ᴹQ. i and the similative suffix ᴹQ. -ndon.
Qenya
ye
preposition. at
ye
conjunction. and
ye-
verb. to be
ye ethen·antas
*and he gives to him (another) it
ye ortalya
is raising
ye sirinyella
*has flown
en ye tá
that is a tee
nikenne karnietta ye mírindanet/s
*I saw its redness and admired it
írima ye númenor
lovely is Númenor
(ye) mólome nakie·nye
(it is) hard work to kill me
-nye
suffix. I
ella nakie nye mólome
it is hard work for you to kill me
etta matie the ye úmahta
his eating it is a nuisance
ha mólome le·nakin(ye)
it is hard work for you to kill me
há ye
that is it, that is so
karie ye mólome
making (things) is hard work
marye
adverb. at home
matie ye mára
eating is (a) good (thing)
mólome nakin(ye)
hard work kills me
tasse ye túro
there’s Túro
ten sí ye tyelma, yéva tyel ar i narqelion
for here is ending, and there will be an end and the Fading
te ye matina
it is eaten
té ye thé (sé) ye hé
this and this [b] and this [c]
marre
adverb. at home
-ie
suffix. perfect suffix
nak-
verb. to kill, slay; to hate
yo
conjunction. and
-ie
suffix. abstract noun
-ie
suffix. gerund suffix
fara-
verb. to hunt
nim-
verb. to seem, appear
um-
verb. to not be, to not do
-le
suffix. abstract noun
-me
suffix. abstract noun
-re
suffix. gerund
-sse
suffix. abstract noun
indon
conjunction. as
lá-
verb. to not be
mane
pronoun. who
nem-
verb. to seem, appear
ná-
verb. to be
to
preposition. in
yu
conjunction. and
A pair of locative variants marre, marye from the Declension of Nouns of the early 1930s, the first derived from ᴹ✶mardasē, and the second from ᴹQ. mar “house” + ᴹQ. ye “at” (PE21/27).
Neo-Quenya: In Tolkien’s later writing, the sound changes producing marre from ᴹ✶mardasē are rather dubious, but I think ᴺQ. maryë “at home” might remain viable as an abstract adverbial form. I would also use maryë in the sense “✱indoors”, inspired by ᴱQ. indoite “at home, indoors” (QL/43).