To rearrange spouses and children you start on the People page, Info box. These wiki pages will demonstrate how this works.
I’m curious to know why births are not automatically in date-order? Apart from any of unknown birth date! Similarly for marriages.
This is how it worked in RM7 as well. If you change the birth dates at Ancestry, or in TMG or FTM, the children are automatically rearranged. but that seems never to have occurred to the coders at RM.