Step 1

To define a new diagram type should be created file {file_name}.config, located in {together_home_directory}/config.
This file has to contain at least one line, which defines new type of diagram:

model.diagramType.{diargam_unique_ID}={diagram_unique_name}

Where:
diagram_unique_ID Any word or number which will be used to sort diagram icons in "New diagram" dialog box. If number is used it has to be greater than 9, because number from 1 to 9 is reserved for standard UML diagram.
diagram_unique_name Any word which will be used to refere to this new type diagram
model.diagramType Predefined construction to define new diagram type

for example:
model.diagramType.sd.SampleDiagram

Step 2

It is possible to define two icons : the small one and big one. The big icon will be used in "New diagram" dialog box. The small icon - on the treeview of the project.

In order to do this, it is neccessary to add following lines to config file:

resource.element.{diagram_unique_name}.name = "{diagram_name_1}"
resource.element.{diagram_unique_name}.diagramName = "{diagram_name_1}"
resource.element.{diagram_unique_name}.icon.small = "{path_to_the_icon}"
resource.element.{diagram_unique_name}.icon.large = "{path_to_the_icon}"

Where:
diagram_name_1 Any name which will be used
diagram_name_2 Any name which will be used in the "New diagram" dialog box.
path_to_the_icon

Any path relative to Together's home path.In order to Together could to find this icons it is neccessary to add images path to Tg_jre12.bat directly after the "-Xbootclasspath". Before the path %TGH% variable has to be added.
For example: -Xbootclasspath:%TGH%\images;

resource.element Predefined construction to define resources: icons, names.

for example:
resource.element.SampleDiagram.name = "Sample Diagram"
resource.element.SampleDiagram.diagramName = "Sample"
resource.element.SampleDiagram.icon.small = "Treeviews/tv-sam-diagram.gif"
resource.element.SampleDiagram.icon.large = "DiagramTypes/SampleDiagram.gif"

See the complete sample config file.