Grid Field Rows with Expandable/Collapsible Section

Try this. 

a!localVariables(
  local!expandedIndex,
  a!forEach(
    items: enumerate(10),
    expression: {
      a!cardLayout(
        contents: {
          a!richTextDisplayField(
            labelPosition: "COLLAPSED",
            value: {
              a!richTextItem(
                text: fv!index
              )
            }
          ),
          a!sectionLayout(
            showWhen: tointeger(local!expandedIndex)=fv!index,
            label: "Transaction History"
          )
        },
        link: a!dynamicLink(
          value: if(tointeger(local!expandedIndex)=fv!index,null,fv!index),
          saveInto: local!expandedIndex
        )
      )
    }
  )
)

There is no OOTB component, but you can easily built such.

This is how they want it to look. They want to show/hide the section below the selected row itself and still list the unselected ones.

OK. Appian does not support that in the OOTB grid component. But you could build a custom grid using columns layouts and then do whatever you want or need to do.

IMHO, I would try to challenge that requirement and try to find a solution that provides the same UX but using a slightly different UI. Staying with the OOTB components saves you a ton of effort and ensures a more consistent UI across apps.

As suggested by other members, no OOTB component to address this requirement, however it can be built easily by using other components with show/hide on condition. 

Yeah, I've built a custom grid (image below). But I think the level of effort to maintain/scale this would be higher compare to when we use an OOTB component and I also think that this kind of design is not ideal for large grids, not sure how it would accommodate large number of columns.

Absolutely!

Hello, can you please share how you did this using columns layout?