Since version 1.11 space property values may reference other space properties. Use the placeholder syntax to create these references. Note that these references are only enforced within the Document Properties Marker Macro of the space homepage (that is: only available for space properties). If you need to refer to a space property value within a page then use the Display Space Property Macro.

version=1.42.73
url=httphttps://example.com/myservice/${version}/apidocs

Note that templates are resolved on request time, while the use of display macros are resolved at document save time. That also includes that documents cannot be queried by resolved template values. So if you need to query documents per property value, you need to use tools to resolve values at save time, not request time.