This is actually a GDL question and here is why.
I checked the library parts used for the Title, and while it is possible to specify a custom Drawing Title, it is not possible to specify a custom Drawing Scale. This means that you would have to modify the GDL script of the Title library part to add this capability.
Laszlo Nagy, Moderator, Site Admin
Get Archicad Tips at https://twitter.com/laszlonagy
AMD Ryzen 1700X CPU, 48 GB RAM
NVidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), WIN10 PRO ENG
AC20-AC24 Loving Archicad since 1995
This depends on the regional version of AC you are using, as different regions have different libraries. In the USA version, the NCS Drawing Titles have an option to show "NOT TO SCALE" rather than the scale; but this text is not editable, so cannot show "NTS".
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.