Short Answer: 'Yes', through (as an) "Add unconnected Person"
That is correct, they will NOT / NEVER be part of YOUR "Ancestral" lines ...
[ ie. the Unconnected Persons, that is ... ]
And, we DO NOT have a 'Tree' (or, 'Trees) in "Family Tree" of 'FamilySearch'.
We ONLY have "Branches", that are interconnected, in this SINGLE "One" World "Tree", for all of us, that is "Family Tree" of 'FamilySearch'.
I hope this helps.
As Brett pointed out, yes you can. But if at all possible, make sure that you add all of the relatives (deceased parents, siblings, grandparents, etc.) that you can with them all hooked together properly as families. That way, when any person in that little tree branch that you create shows up later on the main tree, they will all be marked with research hints identifying the possible duplicates.
The search engines put a lot of emphasis on relationships so having each of those names attached together instead of free-floating in the FSFT will improve the likelihood that their duplicates in the main tree can be found and merged.
Thanks to both of you. I'm anxious to share the information after doing the research.
Susan, bless your heart. When I find stray (to me) records or people who appear to be unconnected to anyone else on familysearch, I often find them because I wonder if they are related somewhere in my lines. I generally add the people, with all of their relations that I can find, because I don't want them put into one of "my" family lines by someone else who finds them and mistakes them as belonging to "my" family. Sometimes I end up adding over 100 people to the Familysearch tree, all unrelated in 15 generations to me. I have rarely ended serendipitously linking them to the part my relatives, but I have on several occasions found them linked to my wife's lines, some as close as 10 generations. If you enjoy family research, these unrelated links are tender mercies you are preparing for others who may eventually link into those lines.
I was surprised that none of the individuals were in the FamilySearch tree. I did finally find one person that was a match by way of a marriage. All of the research was done in order to find someone who would want a photo I have of one of the family members. I'll be sending the research with the photo but decided to add them to the tree as they aren't into genealogy. This activity is what I've been doing during the pandemic.