The headword me/ldontes -- presumably extracted from the first quotation given (which is its only attestation outside the Suda) -- is the present active participle, masculine nominative plural, of the verb me/ldw, I soften by melting (web address 1 below). See also mu 470.
[1] Callimachus, Hecale fr. 322 Pfeiffer.
[2] Homer, Iliad 21.363 (web address 2 below). There, and again here, the participle (masculine nominative singular) is middle voice, meldo/menos. The Suda's gloss uses the active form, me/ldwn. The gloss is similar to that of Aristonicus (see Dickey 2007, pp.18-19) in the scholia ad loc.: *)Aristo/nikos o(/ti a)nti\ tou= me/ldwn, th/kwn "Aristonicus [explained] that [meldo/menos is written] for me/ldwn [or] th/kwn." Note also that the Suda entry uses kni/sh (neuter plural accusative) rather than kni/shn (feminine singular accusative). The feminine form was found in editions going back to Aristarchus (and now in the TLG). Cf. scholia ad loc.: *)Ari/starxos kai\ h( *Kallistra/tou su\n tw=| n kni/shn "Aristarchus and [the edition] of Kallistratos [write] kni/shn with a n. On fat, cf. kappa 1876, kappa 1877.