noun
group item
Computing term for an item that belongs to or represents a group, such as in data structures or user interfaces.
このリストでは、集団項目を展開すると個別の要素が表示される。
In this list, expanding a group item shows the individual elements.
Compound of 集団 (group) and 項目 (item, entry). The exact origin is uncertain; it is a technical term likely coined in computing contexts.