<p>In this paper, we investigate the planar three-center problem with collinear centers, where the centers divide the connecting line into four intervals, referred to as windows. Our objective is to establish symmetric periodic solutions that traverse these windows in a prescribed order and, based on this approach, demonstrate the existence of periodic solutions with as many distinct topological structures as possible. Motivated by the work of Chen and Yu (Ergod Theor Dyn Syst 38(2):566–582, 2018), which establishes the realizability of a class of syzygy sequences by excluding collisions for corresponding minimizers using the local deformation method and provides a lower bound for the number of realizable syzygy sequences. These realizable syzygy sequences correspond to symmetric periodic solutions with distinct topological structures. Building on their results, we further prove the realizability of two new types of syzygy sequences. This leads to a significant improvement in the lower bound estimate for the number of realizable syzygy sequences. It is worth noting that the two types of syzygy sequences may correspond to minimizers where the local deformation method is not applicable. We address this challenge in two ways: One approach involved constructing a new collision-free orbit by connecting two carefully designed Keplerian half-elliptical orbits and then applying the level estimates method to prove the realizability. The other approach involved creating a new set of syzygy sequences by swapping the order of pairs of adjacent elements that differ by one, and proving that this set contains at least one syzygy sequence where the local deformation method is applicable, thereby establishing its realizability.</p>