Enable Edit Mode first (see Edit Mode).

To create a Custom Class as a root class (at the very top level) you make a right-click below the tree and select Add.

This will create a new Custom Class with the default name starting with New Custom Class.

If you click on the class you can rename it in-place.

Or you use Edit from the context menu.

Now you can type in the new name.

After hitting the Return key the Custom Class will be alphabetically ordered within the existing class structure.

You can also create Custom Classes below a custom class by making a right-click on the existing custom class and use Add.

You see the new Custom Class now below the existing one with the default name.

You can again rename the new class.

Lets add another class.

Again, it is added below the existing class.

And we rename it again.

You can add Custom Classes under P&ID classes as well. Again, you just make a right-click on the P&ID class and use Add.

Now the new Custom Class is created below the P&ID class.

And you can rename it again. And it will be ordered too within the other classes.

At the end of the process disable the Edit Mode again (see Edit Mode).
 

Enable Edit Mode first (see Edit Mode).

As mentioned before, Custom Classes will be alphabetically ordered in the same class level of the tree. This means, that you cannot move Dynamic Blocks between Blowers and Compressors.

However, you can move Custom Classes to another level in the tree (up or down). Just use Drag & Drop the class to the class under which the Custom Class should appear. In the image below the Dynamic Blocks class (which is under Equipment) should now be under Engineering Items.

And now the Dynamic Blocks appear under Engineering Items.

If you move a Custom Class which has sub classes...

...the Custom Class and its sub classes will be moved.

At the end of the process disable the Edit Mode again (see Edit Mode).
 

Enable Edit Mode first (see Edit Mode).

If you want to delete a Custom Class you use Delete from the context menu of the class.

Now the deleted class was deleted.

If you delete a Custom Class with sub classes...

...the Custom Class and its sub classes will be deleted.

If there are Custom Objects or Hyperlinks added for a Custom Class, then a dialog will appear.

In this example the Engineering class is empty.

But there is a Hyperlink for the PlantTools Help class.

Now we delete the Documents class.

Since at least one Custom Class has a Custom Object or Hyperlink the following dialog asks you, if you want to Delete Custom Class which will delete the class and all its sub classes no matter if there are customer objects or hyperlinks. With Delete only empty Custom Classes will only delete a custom class if there are no custom objects or hyperlinks for the class. Cancel Deletion of Custom Class will just do nothing.

We use Delete only empty Custom Classes.

The result is, that only the Engineering class was deleted, but the Documents and PlantTools Help class is still there.

Now we delete again.

But this time we use Delete Custom Class.

Now the Documents class is gone as well.

At the end of the process disable the Edit Mode again (see Edit Mode).