Hello there, @userhaider-ali.
I'm here to guide you with changing an asset account to an expense account in QuickBooks Online. You can change the type or detail type associated with an account by following these steps:
To learn more about changing account details in QuickBooks Online, please refer to this article: How to view or change account detail types.
Keep me posted if there's anything else I can do for you. Just add a comment below. Wishing you all the best!