Kids on the spectrum can be so overwhelmed by their environment and by their day, that it can be a balm to have a part of their environment they can personally predict and control. My son loved to arrange and rearrange his favorite figurines/toys/trains over and over in different order, and for him creating that order soothed the “noise” of the day and gave him control over something that represents his topic of interest and favorite things. Making sure they can easily access their favorite toys and an easy surface on which to play with them or arrange them can make all the difference.
Giving them the opportunity to occasionally leave the toys out in the order, or arranged in the manner they prefer, and that they can control, can also be important to kids on the autism spectrum.