How can I insert a search box into a spreadsheet that searches comma separated values in cells?

Deleted ,

The workaround could be to wrap keywords by spaces and search for " apple ", not "apple", like

=IFERROR(
  INDEX($A$11:$A$14,
    AGGREGATE(15,6,
      1/ISNUMBER(SEARCH(" " & $B$1 & " "," " & SUBSTITUTE($B$11:$B$14,","," ")))*
        (ROW($B$11:$B$14)-ROW($B$10)),
      ROW()-ROW($B$1)
  )
  ),
"")

If there are spaces within your keywords you may use any other character instead of space. Please check attached.