It's great to see you here joining this thread, @supplier. 

For me to fully address your concern and provide you with a detailed resolution, may I know what accounts you wish to modify in QuickBooks Online (QBO)? What changes you'll want to make to your accounts? This way, I'll be able to walk you through the process and further provide you with thorough information to help resolve your issue.

Any additional information is much appreciated, as this will help me verify I've got the proper workaround for you.

If you meant modifying your accounts even with the multicurrency turned on, please refer to this article to guide you on how: Set up and use multicurrency in QuickBooks Online.

Feel free to get back to us and leave a reply below for any additional QuickBooks-related concerns. We'd be glad to help you. Keep safe!