Usage notes
Parentheses around a doubled diacritic, as ⟨ẽ̃᪻⟩, indicates a degree of intensity intermediate between that of a single and doubled diacritic. Increasing degrees of nasalization of the vowel [e] are written ⟨e ẽ᪻ ẽ ẽ̃᪻ ẽ̃⟩. Similarly, increasing rounding is written ⟨e ë᪻ ë ë̈᪻ ë̈⟩.
Parentheses are sometimes used around orthographic diacritics, as in ⟨ š᪻ ⟩, a sound that may be either s or š, e.g. in a dialect that doesn't distinguish those sounds, or in a reconstruction where the sound is not clear.
The middle parentheses are use for an overstruck diacritic. In the case of ɫ, the result fused to ꬷ.
Doubling the parentheses means the feature is extra weak, e.g. ⟨ ẽ᪼ ⟩.