On combinatorics of plus-one generated line arrangements

In this note we focus on combinatorial aspects of plus-one generated line arrangements. We provide combinatorial constraints on such arrangements and we construct a polynomial that decodes the plus-one generated property. We present new examples of plus-one generated arrangements constructed by using classical Klein and Wiman reflection arrangements, and we detect, among all known sporadic simplicial arrangements up to $27$ lines, exactly $9$ arrangements that are minimal plus-one generated.