Hi!

Chrome extension will act as Steem Keychain and will ask for the password each time for each action (upvote, subscribe...)?

Once an user unlock his account with his custom password he can sign multiple transactions without having to type his password again until the browser is closed or after 20mn of inactivity.

Desktop apps can be used with a third party application such as Electron application?

Haven't tested but it should be working, the desktop app can call a steem:// based url and SteemConnect desktop app will be triggered.

Do you plan to have a Ionic Cordova plugin version of SteemConnect in the future ? May be interesting for mobile application developers ;)

There is already SteemWallet by Hive account@roelandp which support signing tx with Steem-URI. I've been playing a bit with Cordova lately, I would love to do a mobile app of SteemConnect but it's more like a long term plan.