You can upload the UI JSON configuration files by switching to Classic UI.
To upload UI Configurations:
From the My Profile and Settings dropdown in the Modern UI, click Switch to Classic UI.
In the confirmation popup, click Confirm.
The application reloads the Classic UI.
In the Classic UI, go to System Administration > UI Config Manage.
In the UI Config Manage page, click the Upload icon.
Drag and drop the zip file / JSON file or click Upload File to select from your local system.
Note: If you want to delete the previously uploaded config file, then select Delete mode (Only JSONs).
Click Finish and Close to go back to the UI Config Manage page.
Or
Click Show task details to track the processing status in the Task Detail page.
Click the User Profile > Switch to Modern UI.
In the confirmation popup, click Confirm.
The application reloads the Classic UI.
On the navigation menu, click Help.
In the Help dialog, click Update cache.
The application refreshes and updates the Version Number. You can verify the changes as per the configuration.