If you have substantial amount of coins I would really advise to use HW wallet (apps) or use "Electrum Dash + HW wallet" combination, so that your private keys would never touch any online machine or stored in any kind of internal software db. Electrum Dash works with Ledger and Trezor.

There were some other sites which tried to look like "official" but they had some weird binaries (probably malware) in downloads instead, that's why we created Electrum Dash subdomain on dash.org with latest stable binaries as a quick patch - https://electrum.dash.org/ BUT they are NOT signed (afaik), a proper release process is yet to be established, so use with caution if you plan to store coins without HW wallet there.