www.domain instead of https://domain in WP Multiuser

Hello together,
i had an old 2.9.2 Install and i was unable to get it upgraded, so i let it like that because it was fine, it ran and i didn’t cared. Closed everything with htaccess and I felt really save.
Now i had to change my server.
I couldn’t get the Blog running at all and it took me two days to figure out how to get everything back to ‘normal’
Old Server -> opening all Subs -> Export every Blog -> done
New Server -> Fresh install of WP 3.5.1 -> Do it MU -> Create all Blogs -> Configure them -> Import

Now i am sitting here and i am at an dead end again.
The new Blog is created like https://domain.com/ with Subdomains.

The old Blog was running as https://www.domain.com/ with Subdomains.

I can’t figure out how to get now the “www” back!
Edit (main page) the Values are and not possible to change
Domain https://domain.com
Path /
All other Subs i can change the Path, but here not.

Where do i have to look to get that value changed?

I tried also already the wp-config to set here
define(‘DOMAIN_CURRENT_SITE’, ‘www.domain.com’);
instead of
define(‘DOMAIN_CURRENT_SITE’, ‘domain.com’);

I also had tried to add in the htaccess
RewriteEngine On
RewriteCond %{HTTP_HOST} ^domain\.com$ [NC]
RewriteRule ^(.*)$ https://www.domain.com/$1 [R=301,L]
But here i ended in a circle redirect what couldn’t work. Also no solution.

But how to do then?

Kind Regards