A backup of your widgets should always be done before updating your theme.
Backup Widget Settings
To take a snapshot of all the widget settings for a single site (including all sidebars, etc):
- Go to PLUGINS → ADD NEW
- Search for Widget Importer & Exporter
- Install and Activate the plugin
- Go to Tools → Widget Importer & Exporter and click EXPORT WIDGETS
- Save the file to a safe location.
- This file can be imported on any WordPress install where this plugin is active.
- Be sure your theme and any dependent plugins are setup and content imported before importing widgets – widgets should be the last thing imported to avoid errors and missing content.