How do I insert an expression in the dimension properties text field?

Rhino Rhino for Mac
1

The docs say that I can insert an expression here, but I can’t figure out how. The default content of the field is <> and I can write text around it, but I can’t figure out how to actually use an expression. %<…>% does not seem to work the way the documents say.

Rhino Version 8 (8.13.24317.13002, 2024-11-12)
MacOS Version 12.7.6