You can add parameters which show themselves as flow variables visible throughout. The parameter needs too be called e.g.
-Dknime.constant.double.mypropname=1.2
-Dknime.constant.integer.myint=4
-Dknime.constant.string.mytext= "Hello World"
They will appear as flow variables named
knime.mypropname
knime.mint
Knime.my text
This I think undocumented feature comes from https://github.com/knime/knime-core/blob/master/org.knime.core/src/eclipse/org/knime/core/node/workflow/FlowObjectStack.java
Steve