QB Online doesn't offer any assembly feature. You need to have a 3rd party app to integrate with QBO.

Any advice on third app for this. which will create the new item and post the required accounting entries in qbobline

Explore this one

https://psref.katanamrp.com/katana

Hi @roshanmathews,

I'll share some insight about assembly items. This feature isn't available in QuickBooks Online. However, you can check for a third-party applications that integrates with QuickBooks that'll cater building assembly.

You can visit our website: QuickBooks App Store.

Additionally, here's the link that'll help you manage QuickBooks-related tasks. It has our general QuickBooks topics with articles: Help articles for QuickBooks Online-International.

Please don't hesitate to reply if you have follow-up questions or concerns with inventory items. I'll be around for you. Take care and be safe.