When an existing environment variable is used in the 'Properties Content' field, referenced environment variables are resolved and then re-parsed. In a Windows environment this causes environment variables containing paths to be unusable as the backslashes will disappear.

For example, if JENKINS_HOME is equal to "C:\Program Files\Jenkins" and the 'Properties Content' field contains:

TOOLS_DIR=${JENKINS_HOME}/../tools

TOOLS_DIR will receive the value "C:Program FilesJenkins/../tools" rather than the intended "C:\Program Files\Jenkins/../tools".