Default Value for Post Data

Would like to know if there’s a way for me to set default value for post data; title and content.

i’m thinking to set the title’s default value as something like “{submission_id} post about {user_name}” as my user will post something similar recurringly.

also just wonder if i could set a text area field for user to write then pass the data to the post data field using merge tags {textarea-1}; so that i could format the output for the post data