Explaining

//This is an event function that fires every time an change is made by a user in the sheet.
function onEdit(e) {
  let sh = e.source.getActiveSheet();

  //If current sheet is NOT equeal (!==) to the sheetname AND (&&) range is not equal to H3. then stop the function, So if this is true is automatically points to H3....
  if (sh.getName() !== 'List of Themes' && e.range.getA1Notation() !== 'H3') return;

  //This will get the display values. Be aware!! Ifyou format a number to $50. you will get that (so you working with strings..) use getValues() instead.
  //The values are storred in a 2d array. So an array that holds an array of rows: [["A1","B1","C1"],["A2","B2","C2"],etc..]
  // Then values[0][1] would be: B1. (arrays are zero indexed)
  let values = sh.getRange('A4:F').getDisplayValues();

  //e.value is the value of the event object. (The cell that is changed.)
  switch (e.value) {
  case 'Starry Corridor':
      values.forEach((row, ind) => {
        //If column c is true then show rows else hide...
          row[2] === 'TRUE' ? sh.showRows(ind + 4) : sh.hideRows(ind + 4)
      })
      break;
  case 'Styling Theme':
      values.forEach((row, ind) => {
          row[1] === 'TRUE' ? sh.showRows(ind + 4) : sh.hideRows(ind + 4)
      })
      break;
  case 'Suggestions':
      values.forEach((row, ind) => {
          row[1] === 'FALSE' && row[2] === 'FALSE' ? sh.showRows(ind + 4) : sh.hideRows(ind + 4)
      })
      break;
  case 'Complete':
      values.forEach((row, ind) => {
          row[1] === 'TRUE' && row[2] === 'TRUE' ? sh.showRows(ind + 4) : sh.hideRows(ind + 4)
      })
      break;
  case 'All':
  default:
      sh.showRows(1, sh.getMaxRows())
  }
}