Thank you for reaching out to us here on the Community forum. I can share with you some information about creating transactions using a different GST number or GSTIN.
At this time, an option to add multiple GST numbers is unavailable. The only workaround to issue your bills using is to open a separate QuickBooks account for each tax id.
I can see the importance of this feature for you and your business. I'll pass along the information to our product developers for future updates. Rest assured our engineers will continue to make improvements to the product to deliver the best experiences for all QuickBooks users.
To stay current with the latest QuickBooks news and feature enhancements, you can visit our blog.