This apparently is a "multicurrency" wallet that uses a local version of electrum to work the "btc" functionality:
You can see it just uses the Electrum JSONRPC API to communicate with Electrum from within node.js:
Note, I believe that the full list of available commands is the same as you get when you use help() in the Electrum console:
>>> help()
[
"add_lightning_request",
"add_peer",
"add_request",
"addtransaction",
"broadcast",
"changegaplimit",
"clear_invoices",
"clear_ln_blacklist",
"clear_requests",
"close_channel",
"close_wallet",
"commands",
"convert_xkey",
"create",
"createmultisig",
"createnewaddress",
"decode_invoice",
"decrypt",
"deserialize",
"dumpgraph",
"dumpprivkeys",
"enable_htlc_settle",
"encrypt",
"export_channel_backup",
"freeze",
"get",
"get_channel_ctx",
"get_ssl_domain",
"get_tx_status",
"get_watchtower_ctn",
"getaddressbalance",
"getaddresshistory",
"getaddressunspent",
"getalias",
"getbalance",
"getconfig",
"getfeerate",
"getinfo",
"getmasterprivate",
"getmerkle",
"getminacceptablegap",
"getmpk",
"getprivatekeyforpath",
"getprivatekeys",
"getpubkeys",
"getrequest",
"getseed",
"getservers",
"gettransaction",
"getunusedaddress",
"help",
"import_channel_backup",
"importprivkey",
"init_lightning",
"inject_fees",
"is_synchronized",
"ismine",
"lightning_history",
"list_channels",
"list_invoices",
"list_peers",
"list_requests",
"list_wallets",
"listaddresses",
"listcontacts",
"listunspent",
"lnpay",
"load_wallet",
"make_seed",
"nodeid",
"normal_swap",
"notify",
"onchain_history",
"open_channel",
"password",
"payto",
"paytomany",
"remove_lightning",
"removelocaltx",
"restore",
"reverse_swap",
"rmrequest",
"searchcontacts",
"serialize",
"setconfig",
"setlabel",
"signmessage",
"signrequest",
"signtransaction",
"stop",
"sweep",
"unfreeze",
"validateaddress",
"verifymessage",
"version"
]
The documentation for each one isn't great... but reading the python code here should help: