I've been helping someone trying to create a conlang, and they are insistent that they want seven sonorant approximants. After a bit of desperation, I settled on wa, "vfwa" (which I can't give a good English example of), la, ra, j/ya, and r as in Paris, the way it's pronounced in French. Basically: w, ʋ, l, ɹ, j, and ɰ. I used the alveolar lateral approximate out of desperation, since the other ones sound too similar to their non-lateral counterparts (to me). A dental approximant would feel convenient (since my friend said he didn't like anything uvular, couldn't pronounce pharyngeal, and already used everything glottal we knew of). When I looked up "voiced dental fricative" the results showed ð̞ is what I was looking for. However, there's already a ð sound in the lang, and it sounds identical, to the point of wikipedia using the exact same sound file for both examples. So is there a dental approximant? And if not, what could replace that?
There is, but getting the hang of it and transcribing it isn't easy. It exists in the Kurdish language Hawrami, in the Bantu language Kamba, in another Bantu language Logoori (described by Elizabeth Leung in a Cornell MA thesis), and in Danish, as the lenited voiced lingual stop. In Kamba and Logoori it is basically the way that /j/ is pronounced; it doesn't ever minimally contrast with both [ð] and [j]. You might check the UCLA phonetic archives for examples of Danish "[ð]", or find a Danish speaker.