I have a WAX cloud wallet. And I have to sign all transactions manually by clicking Approve on the modal dialog created by WaxJS.
Is it possible to automate that by calling some API or signing with private key?
Probably you don't want to use the WAX cloud wallet.
Create a real WAX account with the normal EOSIO permission structions, and then you can automate things as you like.
transaction declares authority '{\"actor\":\"XXX\",\"permission\":\"active\"}', but does not have signatures for it under a provided delay of 0 ms, provided permissions [], provided keys