Ok ,seems i was not doing writeall : if i do writeall , seems saved @Tim Edwards

Parameterized devices are not written to disk when they are generated, so yes, "writeall" is necessary to make sure you keep them. This behavior is intentional, as the name of the device is determined by the parameters. So when playing around with parameters, you could end up saving lots and lots of .mag files of devices that aren't even used in the layout. I've been thinking about an implementation where the base name is saved as a file and all the different parameterized variants are saved in the same file. It doesn't really solve the issue but it would prevent a proliferation of files.