Multi Gnome Terminal, like Gnome Terminal, allows for different configuration profiles to suit different uses -- different fonts; different start-up Tabs; background colors; presence, absence or position of scrollbars; and so on. These configuration profiles are known as "Classes". Multi Gnome Terminal's Classes are much more versatile and powerful than Gnome Terminal's.
There is always an active "Class" any time Multi Gnome Terminal is started. If you don't explicitly specify one, you are automatically assigned the built-in "Default" Class.
There are two Class categories: Win Class and Tab Class (each with its own "default" profile). The distinction includes both the scope (i.e. whether the Class pertains to a Tab or a Window), and also which configuration attributes belong to that particular Class. In other words, configuration preferences uniquely belong to one Class or the other. For example, a background image is a Tab attribute only, since backgrounds can be configured individually for each Tab. The same for fonts, font colors, and various other configuration preferences. Most configuration preferences are Tab attributes, which gives a great deal of flexibility.
You can see which preferences belong to which Class from the Tab Preferences and Win Preferences menu selections of the Settings menu. Any changes to the current preferences, will be made to the currently active Class. Again, if no custom Class has been defined, then these changes would apply to the "Default" Class.
If you are upgrading from pre-v1.6.0 versions of Multi Gnome Terminal, this two Class distinction is radically different behavior and will require some re-configuration. Notably, start-up Tabs will have to be re-defined since any previously defined Classes will have been converted to Tab Classes (tclass).
To define a new "Class", invoke the appropriate Preferences dialog-box from the Settings menu. There are separate menu selections for Win Preferences and Tab Preferences. Then, click the New button near the top, and you will be prompted for a new Class name. The Class is created and activated at this point. You also can select whatever other settings and configuration options you prefer (these changes will be made to your currently opened terminal[s], so you can see what they look like). Before closing the Preferences box, be sure to click Apply.
To activate a specific Class at program startup you can use the --tclass (for Tab specific Classes), or --wclass (for Window Classes) command line options (see the Options Section below). Classes of both types can also be specified for start-up Tabs, which is the easiest way of having customized configuration profiles automatically in place when Multi Gnome Terminal is started.
Deleting a Class is roughly the same procedure.
To dynamically change the currently active Class, select either Tab class or Win class from the Settings menu. These will contain a sub-menu listing all defined Classes, from which you can choose one of the selections. Or the same can be done from the control Pop-up menu, accessed with CTRL-RightMouse.
Summary of Multi Gnome Terminal Class features:
Multi Gnome Terminal Classes are a way to save differing user-defined configuration profiles. A user can conceivably define many such profiles.
There is always an active Class in effect. If none is specified, the built-in Class named "Default" automatically becomes the current Class.
Configuration preferences belong to one Class or the other, e.g. a background color is an attribute of the Tab Class. And Toolbar being enabled is an attribute of the Window Class.
Win Class (wclass) attributes are those that logically belong to the entire Window, such as Window title, Tab location.
Tab Class (tclass) attributes are those that can be defined for each Tab, and includes such attributes as terminal font, background color, transparency, bold font color, etc.
Tab Classes effect all terminals (i.e if there are any split terminals), that may exist within that Tab.
Classes can be specified on the command line (--tclass and --wclass) as one method of specifying a Class.
Classes can be dynamically changed from the Settings menu.
Start-up Tabs can be associated with both Class types in Edit Commands.
Class names are case insensitive.
You can use the same name for both a Win Class and a Tab Class. But note that if a Win Class and a Tab Class have the same name, this does not mean they share the same configuration preferences. They can't, since these preferences are unique to one Class or the other.