Hi Shradha,
There are two ways to do this,
1. Create reusable activities such as Java actions separately , combine them as package and publish into app store as Extra capabilities for Excel Module.
2. Override/Add in existing module publish as separate excel module with listed features.
As considering best practices Choice 1 was recommended where we can achieve default and extra features together.
Hope this helps!
Regards,
Sathya Reddy