Hey Is there any way to customize the QuickBooks online by creating a external plugin or bundle and implement in it as like in NetSuite we do?

What kind of feature do you need? You can use a 3rd party app to connect with QBO.

Thanks @Deity Alpha  for your response,

 like I have distributors, so I want to give some extra functionalities to them, so I want customization of QuickBooks.

Can I Create that app in Dot Net and connect to the QuickBooks?

It's a pleasure to have you here today, thoufeeza. We'll point you in the right direction to address this question use QuickBooks Online (QBO) have it utilize inside NetSuite.

Although we provide resolutions to address customers' questions or queries here in the Community space, we have a separate forum where users can post their questions about integrating QBO with other programs or vice versa. Engineers, developers, and other program specialists can also interact with the question and provide the information needed to complete the task. We'll write down the steps to get you going:

1. Visit this link: https://help.developer.intuit.com/s/
2. Choose QuickBooks Online.
3. Select Ask a Question.
4. Log into your existing Intuit Developer Account or create a new one.
5. Provide a brief description of your concern.
6. Click Ask.

In addition, we highly recommend checking this handy article that talks about the compatible app that works best with QBO: Apps that work with QuickBooks Online.

Feel free to comment below if you require assistance managing third-party integrations inside the program. Our team is always ready to lend you a helping hand in resolving your concerns. Keep safe.