My board requires milling outlines, and I am not sure if this is:
A. Ok under your production guidelines.
B. If my way of doing it in KiCad is how you expect me to do it
I simply added 0.8mm slots on the PCB Outline layer. KiCads GerberViewer accepts that. But it is not so clear in your online viewer.
If i click right away on the Drill-layer in your online viewer the result looks like this:
https://i.imgur.com/1vj5oOg.png
If i click on the outline layer and then on the Drill-Layer the result looks like this:
https://i.imgur.com/B4Dd8sy.png
The used Gerber/drill-file archive: https://www.file-upload.net/download-12948186/production.zip.html