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).
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.