Hi folks,
The configuration file which you want to make offline can be a plain text file [made with notepad in windows or VI editor in unix] and later you can use to upload it to the box. Copy the file to the local router, and then load the file into the CLI. After you have loaded the file, you can commit it to activate the configuration on the router, or you can edit the configuration interactively using the CLI and commit it at a later time.
You can also create a configuration while typing at the terminal and then load it. Loading a configuration from the terminal is generally useful when you are cutting existing portions of the configuration and pasting them elsewhere in the configuration.
To load an existing configuration file that is located on the router, use the load configuration mode command:
[edit]
user@host# load (factory-default | merge | override | patch | replace | set | update) filename <relative> <json>
To load a configuration from the terminal, use the following version of the load configuration mode command. Press Ctrl-d to end the input.
[edit]
user@host# load (factory-default | merge | override | patch | replace | set | update)
terminal <relative> <json>
https://www.juniper.net/documentation/en_US/release-independent/topics/task/configuration/ex-series-configuration-uploading-cli.html
https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/junos-software-configuration-file-loading.html