Cute interface; however, I've not tried it. I'm leaving these suggestions not for me but for you in case you want this thing to be more than a fancy connection manager.
Write up some goals for the product. What is the intention for its existence? What problems will it try to solve and what problems will it not try to solve?
Write some documentation.
Consider usability (perhaps you've done this already; however, I wouldn't know since I've not used it)
Consider what happens when a person stores several connections and wants to move those settings to another computer (i.e. dotfiles)
How will you deal with dotfiles (i.e. XDG?)
Proxies, TLS, etc
Keyboard shortcuts (think, slack)
Automation & Scripting (will this be useful for repetitive tasks?)
Cute interface; however, I've not tried it. I'm leaving these suggestions not for me but for you in case you want this thing to be more than a fancy connection manager.
That's all I can think of for now. Hope it helps.