Hi @Britney_Schindler. Welcome to the forum!
Unfortunately, no. When creating a portfolio, you will need to search and select each project one at a time. There is a product feedback request to enhance this option where you can upvote: PORTFOLIO - Adding projects (various methods)
Also, for a 3rd party option, another Certified Pro-Forum Leader (@Bastien_Siebman) has created a great free tool to upload all projects at once withing an Org or Team.
https://minimalist-work.com/asana/global-workload
In regards to having to duplicate your account (Portfolio) for everyone…this does NOT need to be done. Simply either share the Portfolio link with other users or invite them as members. Have a look at the Asana guide article below for more details. Hope this helps!