@Thilak Baskaran, Thanks for posting in Q&A.
From your description, I know you want to assign a category to an Intune Application using the PowerShell script.
Based on my research, here is a link with useful information you can refer to.
https://memv.ennbee.uk/posts/creating-assigning-app-categories/
Non-official, just for reference.
Hope it can help you.
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