!DATASOURCE LINE
From iMacros
Specifies the line in the datasource which is used for input.
Contents
Value

Any positive integer.
Set By
[ ] Internal
[X] SET
Internal means that the iMacros program itself sets the value of the variable during program run. SET means that the user can set this value via the SET command inside a macro.
Examples
SET !DATASOURCE_LINE {{!LOOP}}
More examples here.
See Also
!DATASOURCE for selecting the input file