Each field in your invoices has a maximum number of characters as per the default format in QuickBooks. You can send feedback to our engineers. This way, they can check and consider adding it to their future update release.
This data is a relational database. That means the data is kept in Fields and these are Defined. They get defined as Numeric, or Date, or Alpha-numeric, and they are assigned Limits in the Relational database tables.
Even though you can Stretch, for instance, the Customer Name in the Customization of the template, the Data Table holds the Field Size and definition.
This is programming. This is the Database Structure. If you really want to see it, you can see it here: