Unless you're doing something odd in MS-Word then the answer is, "No, not really," if you mean some identifying character for start and end of line.
Word, like most word processors, flows text so that it fits between your specified margins, using your specified spacing, without the need to hit Enter to start a new line (doing so typically starts a new paragraph).
There are commands to take you to what is the start and end of the line as currently flowed: Home and End, respectively. Single key presses from anywhere in that line of text.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
Any idiot can face a crisis. It's the day-to-day living that wears you out.
~ Anton Chekhov