Inspired by this answer here is my question: How can I write a interdental lateral in phonetic transcription (IPA preferred, but not a necessary requirement, other wide spread phonetic notation systems are also welcome)?
extIPA gives you these options:
- Voiceless interdental lateral fricative: ɬ̪͆
- Voiced interdental lateral fricative: ɮ̪͆
- Voiced interdental lateral approximant: l̪͆
However, I find these diacritics a bit of overkill, especially given American English /θ, ð/ are also usually interdental but never transcribed with these diacritics anyway. I bet just [ɬ̪, ɮ̪, l̪] (or even [ɬ, ɮ, l], unless the language contrasts interdental with (post)alveolar) would suffice in most occasions.
With a different idea, interpreting the interdental lateral as a lateralized th sound and using the IPA character ˡ (raised l) for lateral release: /ðˡˤ/. This sound is attested according to Wikipedia for some Modern South Arabic language or some Southern Arabic dialect.