Type this in your chrome’s address bar:
Then filter by ‘Parallel downloading’:
Few words of caution while working with Chrome flags-
Google chrome flags are experimental features and you should be using it with caution. Since these features are experimental, they can be either moved as permanent feature or can be removed from the list.
In case you are not able to find any of the above mentioned experimental chrome flag in your browser, there are good chances that Google has already moved it into Chrome or has removed, based on user feedback.