Form to temporary table before saving in database

Hello,

I am trying to have a form with 3 fields (input, 2 date pickers), which show a new line once the last date picker is filled. Then when all th datas are filled I want a button sending the information in my database.
I have read about custom states as a list, schedule API , but I am still confused what is the best solution to implemente.
Someone could help me please?