The verb G. mara- or (m)bara- “dwell” appeared in the Gnomish Lexicon of the 1910s (GL/56), clearly based on the early root ᴱ√MBARA “dwell” which was blended with ᴱ√MARA (QL/60, 63); the (m)bara- form might be a variant of G. bar(n)a- “dwell in, till (land)” (GL/21). Early Noldorin Word-lists of the 1920s instead had (infinitive) ᴱN. meriad “to dwell, live, stay” (PE13/150), apparently still based on ᴱ√MAR. In Tolkien’s later writings, however, the “dwell” root was consistently √MBAR.

Neo-Sindarin: Given the later form of the root, the Gnomish verb might be salvaged as ᴺS. bar- “to live, dwell, stay” for purposes of Neo-Sindarin, a cognate of Q. mar- “abide” (UT/317), though you may just want to use attested [N.] dortha- “to dwell, stay” from the 1930s (Ety/NDOR).