Each node can be satisfied by at least 2 in portal crew. Solutions with only one node will not be the answer. NOTE: This site is not always up to date, but unless there was a portal update announced within the last few days, the in portal rule can be trusted. And if there was a portal update that is not accounted for yet, then new in portal items would still be in the results, they would just inaccurately have the "Not in portal" alert.
It is extremely likely that any duplicate options for the unknown tag must all be used in some node (e.g., if there are 2 "Vulcan" tags in the unknown trait options, then 2 of the nodes would use the "Vulcan" trait).
Often, nodes are displayed in alphabetical order, which means that the unknown traits would come after the known ones. There HAVE been counter-examples for this rule, but it is still true for the vast majority of nodes.
NOTE: In some cases, it is possible to perform advanced deductions (e.g. All the characters listed under the second node have the "Pilot" trait, and there is only one "Pilot" tag in the optional traits, so the other nodes cannot have "Pilot"). If you are attempting such a deduction, it is advised to uncheck the "Alphabetical Trait Rule" first. [ dismiss hint ]