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The Save Button Label can be customized for each step in your workflow. For example, you can change the button text to Save for Later on step 1 of your flow and then to something different on step 2. This will help users understand what to do if they want to save a partially completed flow. Designers should click here for the details.
The Currently the ability to change the Save button label for forms will be available in a future releaseis only available for flows.