Nānāccaya appears only here. I take it as nānā + accaya, “excessive variety”, which suits the context. The commentary takes it as a variant of nānācaya, “consisting of various mixtures”.

Elsewhere madhuragga means a “sweet tip” (SN 1.71:3.4) or the “superbly sweet” mango (Ja 511:6.4). | Sour, sweet, and bitter flavors are remembered at Thag 16.2:8.1.

“Hint” here is nimitta, found in the same sense at AN 5.80:6.3 and DN 16:3.4.1. As usual in early Pali, nimitta is used in the sense of a feature or quality that, when focused on, promotes the growth of similar or related qualities. If the Master’s hint were taken, the cook would serve more of what he likes and less of what he dislikes. Similarly, a meditator who takes the mind’s hint will experience a growth of wholesome and decline of unwholesome qualities.

Here we see the primary purpose of satipaṭṭhāna, namely, as the basis for samādhi (MN 44:12.3).