There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
líne
noun. cobweb, cobweb; [ᴱQ.] cotton, thread
filet
noun. cobweb
A word in in the Declension of Nouns of the early 1930s glossed {“fern” >>} “cobweb” (PE21/33 and note #3). Its initial gloss was probably a later iteration of ᴱQ. filqe “fern” from the Qenya Lexicon of the 1910s (QL/38), and in later writings filit (filik-) was a word for “small bird, sparrow” (Ety/PHILIK; PE21/56), so this was likely a transient form.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun for “cobweb” in The Etymologies of the 1930s derived from primitive ᴹ✶slignē under the root ᴹ√SLIG (Ety/SLIG).
Conceptual Development: In the Qenya Lexicon of the 1910s Tolkien gave ᴱQ. līnẹ “thread, cotton” under the early root ᴱ√LI+ya (QL/53).
Neo-Quenya: This word is somewhat questionable, since in later writings, Tolkien derived spider words from √ungu-. However, I prefer to interpret ᴹ√(S)LIG as having to do with threads for purposes of Neo-Eldarin, and “cobweb” could be from a sense “collection of threads”. With this interpretation, I think it is also plausible to include the sense “cotton” from Early Qenya, though for “thread” I’d use other words like Q. ipsin or [ᴹQ.] lia. Helge Fauskanger suggested (QQ/líne) that this word should be ✱hlíne given primitive initial sl-, but there is another primitive form ᴹ✶ligā under the root, so perhaps the Quenya derivatives were (a) based from a variant root ᴹ√LIG or (b) reflect the Third Age Quenya pronunciation as voiced l (LotR/1114).