The Texas legislature meets every other year to handle the legislative processes for the State. Every two years new laws come out or old laws get changed. Some of those changes effect Divorce and Custody matters.
The Legislature changed the law regarding what's required if you want to modify an old custody/visitation order. Now, if you want to change who is the primary parent or create/change/eliminate a primary residence restriction, then you have to include a statement with your initial court pleadings to establish how the child(ren)'s physical health or emotional development would suffer unless the Judge granted your requested changes. Previously, this statement was only required if you wanted to change the primary residence designation, i.e., the child switch which parent they lived with during the school week. See Texas Family Code 156.006. Now the law includes both.
Bottom line is if you are trying to change your old custody or visitation orders and are trying to change the child(ren)'s primary residence or the geographic restriction designation, then you would have to include a sworn statement alleging the potential harm to the child(ren) you are trying to avoid with the modification. Without such a statement your case might not get a hearing and might be dismissed out of hand before you can reach any real issues, causing delay and additional expense.