By default, all the repertories accessed in ArcPad are recorded and a list of data storage locations are provided to ArcPad in drop down lists automatically generated.
These drop down lists become larger as ArcPad is used. A list of the last projects opened is also listed when starting ArcPad.
This information is not stored but rather, the list in the Add Layer(s) Path dropdown is generated dynamically by ArcPad using standard Windows APIS. ArcPad sets a flag and Windows remembers the recent documents. This is not exposed as a variable.