The listwalletdir RPC returns a list of wallets in the wallet directory
listwalletdir none
*bitcoin-cli help listwalletdir
listwalletdir Returns a list of wallets in the wallet directory. Result: { (json object) "wallets" : [ (json array) { (json object) "name" : "str" (string) The wallet name }, ... ] } Examples: > bitcoin-cli listwalletdir > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "listwalletdir", "params": []}' -H 'content-type: text/plain;' http://127.0.0.1:8332/