Hello there, @humayun3871!
There are several functions you can utilize in organising your subsidiaries. First, the Class or Location tracking and the Project feature. You can read through the following articles below to learn more:
Lastly, here are articles you read for ideas to help manage your account and related tasks: Help Articles for QuickBooks Online.
If there's anything else that I can help you with, let me know int he comments. I'll be here to lend a hand.
