Based on my investigations... the "Save" option on the "Send" tab in Android Electrum (the little diskette icon), simply saves the "invoice" into your wallet file... It is not used like the "save" option in the desktop client for being able to export transactions for signing offline.
...
"invoices": {
"1dummyBitcoinAddress": {
"hex": "22291xxxxxxxxxxxxx[redacted]xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx6f6f2a00",
"requestor": null,
"txid": null
}
},
...