Looks like Spreadsheet, though tagged Excel : Question

const onOpen = () => {
    SpreadsheetApp.getActive().addMenu("Custom", [
        {
            name: "q256332",
            functionName: "q256332"
        }
    ]);
}
const q256332 = () => {
  const mark = "○";
  const range = SpreadsheetApp.getActiveRange();
  let table = range.getValues();
  const header = table.shift();
  SpreadsheetApp.getActiveSheet().getRange(range.getRow()+table.length+2,range.getColumn(),table.length,2).setValues(table.map(item=>[item[0],(item.reduce((a,c,i)=>c===mark?a.concat(header[i]):a,[])).join(",")]));
}

From


	A	B	C
A			○
B	○	○
C	○	`

To


A	C
B	A,B
C	A