Simple download manager based on Youtube-dl
Issues
The first one is the use of the or operator. If you wish to compare a variable with two values, you will have to write the comparison operator twice.
For instance,
if Login_ == 'y' or 'Y':
  ...

should be write as:
if Login_ == 'y' or Login_ == 'Y':

Also, it seems you are returning from the Downloader function before iterating though all links (whenever the first process finishes correcly):
...
if result == 0:
  download_count += 1
  # This will return after one commad executes successfully
  return('\nReturned Value', result)

Code style
Now, regarding code smells and style, in python there is PEP-8, a general guide for code style.
For example, functions/methods and variable names should start with lowecase (Login should be called login).
Also, in the Login function, you are assigning the values of the url and login_route parameters to URL and LOGIN_ROUTE but they do not seem to serve for anything special. You could just use the function's parameters directly:
...
headers = {
 'User-Agent': '',
  'origin': url,
  'referer': url + login_route,
}
...
csrf_token = request_session.get(url).cookies['csrftoken']

Same goes for Page_URL in Scraper.
Moreover, return should be used as a statement, rather than with function notation:
def myFunction():
  return 0

Is better than:
def myFunction():
  return(0)

Readability
Lastly, I would say this assignment in Login is not quite readable:
msg = (
        f'You have logged in successfully {login_request.status_code}' if login_request.status_code == 200 else
        f'Error {login_request.status_code}' 
    )

Language features are there for when they are useful, but readability is key and should be kept in mind. I would write that assignment as a simple if-else:
if login_request.status_code == 200:
  msg = f'You have logged in successfully {login_request.status_code}'
else:
  msg = f'Error {login_request.status_code}'