USER INTERFACES FOR USING SHARED DATABASES FOR MANAGING SUPPLEMENTAL PAYMENT SOURCES

User devices are disclosed for managing a plurality of supplemental payment sources of a user. One method includes: generating and displaying a user interface prompting a user to input: an identifier of a primary payment source account for applying resources to transactions originating at one or more merchants, the primary payment source account being accounted for in a first data structure of a shared ledger and having its identifier linked with one or more supplemental payment source accounts; identifiers of one or more supplemental payment source accounts for applying resources to transactions originating at one or more merchants, the supplemental payment source accounts being accounted for in second and subsequent data structures of the shared ledger; and preference settings for applying resources of the primary payment source account and the supplemental payment source accounts to transactions, based on identities or categories of merchants involved in the transactions.