Welcome to the "Community.FamilySearch" Forum ...
As an aside ...
You can have up to x100 Sets of Parents - as if, that was ever needed ...
And, here is the "Pop-Up" (ie. "Modal") 'Window' to add the TYPE of "Parent-Child" Relationship ...
Here are some "Knowledge Articles" in 'FamilySearch':
How do I add step, adopted, and foster parents to a child in Family Tree?
How do I add step, adopted, and foster children to parents in Family Tree?
How do I specify biological, step, adopted, and foster relationships in Family Tree?
I hope this helps.