Now, that's a completely different question. An environment variable, to me, is something like %root or another variable that you set at the operating system level. An environment variable would NOT be a value from a data set, in my interpretation of "environment" variable. On the other hand, I could set a "SAS environment variable" in my AUTOEXEC.SAS file -- something like &PATH that would be my location for writing files.
In fact, there's a SYSGET function that allows you to get the value of an operating system environment variable. And, yet, there's no Wizard to invoke SYSGET, you would have to do that in code. %SYSFUNC, is a Macro function that allows you to invoke a data step function....so for example,
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footnote "Created on: %sysfunc(today(),mmddyy10.)";
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would use the today() function to grab today's date and format it with the mmddyy10. format and use that value in the footnote.
The answer to your question depends on whether you want the value from a DATASET variable in your footnote or the value from an ENVIROMENT variable in your footnote. Tech Support can help you in this regard.
cynthia