Export
A transport is a snapshot of an app's definitions: pages, themes, functions, storages, templates and schemas. Exporting never touches runtime data, and never changes anything here.
One service, chosen objects
Narrower and easier to review. A type with no object picked exports whole.
Service
ui
core
Format
UMODL
CMODL
JSON
Transport name
Recorded inside the file. Blank uses the app code.
Object types
Tick nothing for every object the service holds.
Pages
Themes
Styles
Functions
Schemas
URI paths
Storages
Templates
Functions
Schemas
Event actions
Event definitions
Connections and notifications are not in any transport, so an app restored from one arrives without them.
The security half does not travel
Roles, profiles, app properties and the registration rows are NOT in a transport. The security service's transport is stubbed out, so the security.json inside a whole-app file is empty and there is nothing to import back. Recreate them on the target: roles and profiles under Organization, and the rest on the Sign-in, Registration and Policies tabs.
Nothing to export until that service is implemented.
Or the whole application
The ui definitions and the core definitions in one file, which is what New app accepts. On a large app this can time out at the gateway, in which case take one service at a time above.