Creating New Catalogue Type

No FileName is selected, so it doesn't know in what XML to store the new Type.

Thanks Koert. so where exactly are these XML stored in the dataset...I mean the path. I need to create a new type for Door (Access Panels) and wall (demountable wall)

I look forward to hearing from you

thank you

That depends on your configuration.

The Catalog Types and DataGroup definitions are usually located in "datagroupsystem".
The actual Catalog Items (and custom catalog types and catalog type extension files) are in "datagroupcatalogs".

The value of the variable DG_PATH will show you the possible locations of the datagroupsytem files.
The value of DG_CATALOGS_PATH will how you the locations of the datagroupcatalogs.

This can be a combination of System-, Base-, Company-, ProjectDataSet and other DatasetExtensions.
You could create these files in any of the configured path locations, but I'd recommend rigorously managing and naming those files in their appropriate locations.
If it's for a specific project, put it at the projectlevel and make sure you select the file at the projectlevel when adding Items.

Copying these Types to another Project could then be a matter of simply selecting the right projecttemplate when you create a new project.
Adding things to your BaseDataSet (e.g. DataSet_US) will work, but I'd recommend against it as you'll have to take extra care to not lose these when upgrading the Program and base (Bentley) DataSet.

Normally you would find those in:
WorkSpace\BuildingDatasets\<yourdatasetname>\datagroupcatalogs

You can create new xml's too.