No. Each curator profile connects to exactly one Spotify account, the one it signed up and connected with. There's no way to attach a second Spotify account to the same profile.
Team members don't add a Spotify account
Adding someone under Settings → Users lets another person help manage your existing profile, but it doesn't connect their Spotify or surface their playlists. The profile keeps showing only the playlists owned by the one Spotify account it's connected to.
Why there's no "Connect Spotify" button once you're connected
The connect option only shows when no Spotify is linked yet. Once a profile has a Spotify connected, that button is replaced by a disconnect option, so not seeing a connect button is expected, not a bug.
I want to use a playlist from a different Spotify account
Set that account up as its own curator profile: create a separate SubmitHub user account, connect that Spotify to it, and apply at submithub.com/apply. Each Spotify account gets its own curator profile.