"Edit Query Text" query text doesn't match the actual query in 2017 RTM
In 2016 & prior versions, when looking at a stored procedure's execution plan, if you right-click on the plan and click Edit Query Text, you get the full text of a stored procedure. In 2017, it's clipping out parts of a stored procedure, and formatting the query differently.
I was informed that query plan text was always truncated at 4000 characters, regardless of SSMS version. Is that different than what you are seeing?