Hello, Tim!
I don't know what the configuration for those actions are, but yes, that should work. :)
As long as you have the right RecordID for your estimate, it should be fine.
By the way, in the future, when you get more comfortable with customizing, I would find a way to make it more robust and future-proof by creating a screen that will allow the user to choose what items gets added to the estimate lines.
Guessing from what you have in the action set, it looks like what you are inserting is hard coded into the actions.