The type of a group can be specified using the :class property at the
beginning of the class specification, e.g., [:class transient-columns
...] in a call to transient-define-prefix.
transient-child class is the base class of both
transient-group (and therefore all groups) as well as of
transient-suffix (and therefore all suffix and infix commands).
This class exists because the elements (or “children”) of certain groups can be other groups instead of suffix and infix commands.
transient-group class is the superclass of all other
group classes.
transient-column class is the simplest group.
This is the default “flat” group. If the class is not specified explicitly and the first element is not a vector (i.e., not a group), then this class is used.
This class displays each element on a separate line.
transient-row class displays all elements on a single line.
transient-columns class displays commands organized in columns.
Direct elements have to be groups whose elements have to be commands or strings. Each subgroup represents a column. This class takes care of inserting the subgroups’ elements.
This is the default “nested” group. If the class is not specified explicitly and the first element is a vector (i.e., a group), then this class is used.
transient-subgroups class wraps other groups.
Direct elements have to be groups whose elements have to be commands or strings. This group inserts an empty line between subgroups. The subgroups themselves are responsible for displaying their elements.