Option to add "www" pair to beginning of block list domains

It would be great if, after adding a list in settings and updating, pihole would automatically add a www version of all domains in list, in order to block both version of domains. Or it could be an option in settings.
This is useful if you use a third part list and you would keep it update without modifying it.

Would it be more effective to feedback to the list owner to include the www version of each domain as appropriate? Then the list is fixed at the source and not altered in any way by Pi-Hole.

It would.... if it could be easily updated by the owner... what if the lit has no owner? or if it's a collaborative one and it's too long to update all domain? doing this option to pihole could be a simple solution.

If it's too long to update, how would Pi-Hole be able to do it?

while importing the list just adds a new line for every original line with www. before...

It is not the Pi-hole's job to patch the block lists that are given to it. List maintainers can do this work more effectively, which makes Pi-hole simpler and more efficient than adding a second entry for every domain it gets from the block lists.