Invite someone
Under the organisation's Members or Invitations. Needs organisation-admin access.
Change someone's role
Under the organisation's Members. Needs organisation-admin access.
Limit someone to certain sites
Site scope decides where a member can work. It changes nothing about what they can do.
Edit a role's permissions
Change what a role means in your organisation. Under the organisation's role settings; needs organisation-admin access.
Remove someone
Under the organisation's Members. Needs organisation-admin access.
Create a team
Under the organisation's Teams. Needs organisation-admin access.
Manage billing
Under the organisation's Billing.
Create an API key
Under Settings → API keys.
Manage your sessions and notifications
Both are under Settings, and both are yours — they follow you across every organisation you belong to.