I have a very small ask that would serve a lot of use cases but isn’t actually ZEC-specific at all: I want Zcash to have a wallet app that can categorize specific transactions in a GNUCash (Intuit QuickBooks/Microsoft Money) style income or expense double-booking accounting scheme.
Edge Wallet can do this (see Bitcoin Accounting Made Easy - Edge ) but Edge doesn’t support rotating addresses for Zcash wallets (i.e., it will not auto-rotate your Sapling or Orchard address after you use it to receive a payment). Zashi supports rotating addresses but its transaction metadata scheme is limited to only a free-form text field of limited length.
In my use case (see the workshops I am running for Zcash education initiatives reaching vulnerable populations, Supporting Financial Privacy Education for At-Risk Communities - #9 by fabacab ), one of the single most frequently asked questions I get is “how do I know which transaction is for what?” While having built-in “contact lists” to label addresses is useful for that side of the question, the other half, having a built-in way to categorize income and expenditures, is still largely missing from most cryptocurrency client applications, which creates far more friction for adoption than I believe most people are currently recognizing.