Specifically, it adds an address into the wallet.

Easy to test now thanks to https://github.com/bitcoin/bitcoin/pull/14410
```
diff --git a/test/functional/wallet_importmulti.py b/test/functional/wallet_importmulti.py
index 9ba6860..bff37b2 100755
--- a/test/functional/wallet_importmulti.py
+++ b/test/functional/wallet_importmulti.py
@@ -95,6 +95,7 @@ class ImportMultiTest(BitcoinTestFramework):
         assert_equal(address_assert['iswatchonly'], True)
         assert_equal(address_assert['ismine'], False)
         assert_equal(address_assert['timestamp'], timestamp)
+        assert_equal(address_assert['ischange'], True)
 
         # ScriptPubKey + internal + label
         self.log.info("Should not allow a label to be specified when internal is true")
```

std::string strTime = FormatISO8601DateTime(it->first);
        std::string strAddr;
        std::string strLabel;
        CKey key;
        if (pwallet->GetKey(keyid, key)) {
            file << strprintf("%s %s ", EncodeSecret(key), strTime);
            if (GetWalletAddressesForKey(pwallet, keyid, strAddr, strLabel)) {
               file << strprintf("label=%s", strLabel);
            } else if (keyid == seed_id) {
                file << "hdseed=1";
            } else if (mapKeyPool.count(keyid)) {
                file << "reserve=1";
            } else if (pwallet->mapKeyMetadata[keyid].hdKeypath == "s") {
                file << "inactivehdseed=1";
            } else {
                file << "change=1";
            }
            file << strprintf(" # addr=%s%s\n", strAddr, (pwallet->mapKeyMetadata[keyid].hdKeypath.size() > 0 ? " hdkeypath="+pwallet->mapKeyMetadata[keyid].hdKeypath : ""));
        }
    }
    file << "\n";
    for (const CScriptID &scriptid : scripts) {
        CScript script;
        std::string create_time = "0";
        std::string address = EncodeDestination(scriptid);
        
        auto it = pwallet->m_script_metadata.find(scriptid);
        if (it != pwallet->m_script_metadata.end()) {
            create_time = FormatISO8601DateTime(it->second.nCreateTime);
        }