Hi Pradeep,
Thank you for reaching out. There is no direct API equivalent to that slider. However, you can follow
this guide for generating forecasting metrics for a proposed campaign based on a specific budget (or
here if you are using Google Ads API). You can create a budget for a smart display campaign the same way you would for any other campaign. See
here for more information on creating Smart Display Campaigns in AdWords API (or
here for Google Ads API).
Regards,
Mitchell
Google Ads API Team

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