Thanks for your answers!
But... I can't get it to work when the shapefiles are located in a folder somewhere else than a subfolder relatively speaking deeper down from the executing workspaces.
Example.
C:\\fme_rocks\\WorkspaceRunner\\Workspacerunner.fmw and workspacetoberun.fmw ---> C:\\fme_rocks\\WorkspaceRunner\\INPUT\\shapefile1.shp and shapefile2.shp --> this works
C:\\fme_rocks\\WorkspaceRunner\\Workspacerunner.fmw and workspacetoberun.fmw ---> C:\\datadir\\subfolder\\shapefiles\\shapefile1.shp and shapefile2.shp --> this is what I need to work and is what I can't get to work.
This is how i try to reference my shapefiles within the workspacerunner:
""C:\\whatever\\NYKO2.shp" "C:\\whatever\\NYKO3.shp""
The log-error:
Shape Reader: Failed to open dataset 'C:\\whatever\\NYKO2.shpC:\\whatever\\NYKO3.shp' which is neither an existing file nor directory
If a friendly soul would like to look deeper into this you can find an isolation of this behavior attached to this message (created with FME2019.0 64-bit)