Add Table Later to Database First Project

Hello 

I have a project with Database First Migration 

I used the below code from PM to scaffold the DB 

Scaffold-DbContext "Server=(localdb)\mssqllocaldb;Database=Blogging;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models

now I want to create a table, I tried to add it as New model class but when I do the command 

add-migration -context mycontext 

It is not adding it to migration file

1- Do I have to add it to Snapshot file? I added it but when I process add-migration command, it is removed from Snapshot 

2- Can I create the table in SQL and then scaffold it again, only for the new table.

Any Idea?