VASSAL Reference Manual
A Marker trait is used to mark a game piece permanently as always having a particular Property. Unlike many other types of Properties that can be configured on and by pieces (e.g. Dynamic Properties), a Marker’s value cannot change during play. In other words, it is like a constant rather than a variable in programming.
Setting a property does not in itself give a game piece any particular behavior. The property must be recognized by some other trait or class in the module. Markers can be referenced in Global Key Command traits and Game Piece Layer traits and in many other traits within Expressions and Message Formats.
You can combine multiple name/value pairs by separating the names and values with a comma (','). To use a literal comma in a name or value, precede it with a backslash ('\').
EXAMPLE: A Marker with property name "owner" and property value "sigmund" would return "sigmund" from getProperty("owner") or $owner$. Use commas to set multiple properties with a single Marker. A Marker with name "owner,status" and value "sigmund,unknown" would also return "unknown" from getProperty("status") or $status$.