A proof of concept to make sure that an NSButton with setKeyEquivalent:@"\r" next to an NSTableView responds to pressing Enter/Return when the table has the focus

main.m

// To compile, add AppKit.Framework to the required frameworks for the project

// Includes and modifies code from -
// https://github.com/eonil/CocoaProgrammaticHowtoCollection/tree/master/ComponentUsagesInObjectiveC/FileDropIntoTableView
// Created by Hoon H. on 2014/06/13.
// Copyright (c) 2014 Eonil. All rights reserved.

// https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/ui/cocoa/task_manager_mac.h
// https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/ui/cocoa/task_manager_mac.mm
// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found at https://source.chromium.org/chromium/chromium/src/+/main:LICENSE;drc=48340c1e35efad5fb0253025dcc36b3a9573e258;l=0

#import <Cocoa/Cocoa.h>

@interface TestWindowController: NSWindowController <NSTableViewDataSource>
@end

@implementation TestWindowController {
  NSWindow *window;
  NSTableView *tableView;
  NSButton *_endProcessButton;
  NSScrollView *scrollView;
}
- (instancetype)initWithWindow:(NSWindow *)window {
  self = [super initWithWindow:window];
 
  window = [[NSWindow alloc] init];
  window.delegate = self;
  [window setContentSize:CGSizeMake(350, 200)];
  [window makeKeyAndOrderFront:self];

  NSTableColumn *c1 = [[NSTableColumn alloc] init];
  c1.headerCell.stringValue = @"Task";

  tableView = [[NSTableView alloc] init];
  tableView.delegate = self;
  [tableView addTableColumn:c1];

  _endProcessButton =
      [NSButton buttonWithTitle:@"Kill"
                         target:self
                         action:@selector(killSelectedProcesses:)];
  [_endProcessButton setKeyEquivalent:@"\r"];

  scrollView = [[NSScrollView alloc] initWithFrame:NSMakeRect(10, 50, 300, 150)];
  NSView *contentView = window.contentView;
  scrollView.documentView = tableView;
  [contentView addSubview:scrollView];
  [contentView addSubview:_endProcessButton];
  tableView.dataSource = self;
  return self;
}

- (id)tableView:(NSTableView *)tableView objectValueForTableColumn:(NSTableColumn *)tableColumn row:(int)rowIndex {
  [tableColumn setEditable:NO];
  return [NSString stringWithFormat:@"Tab %d", rowIndex];
}

- (NSInteger)numberOfRowsInTableView:(NSTableView *)tableView {
  return 5;
}

- (IBAction)killSelectedProcesses:(id)sender {
  NSString *s = [NSString stringWithFormat:@"%d", tableView.selectedRow];
  [[NSAlert alertWithMessageText:s defaultButton:s alternateButton:@"" otherButton:@"" informativeTextWithFormat:@""] runModal];
}

@end

@interface BoilerplateApplicationController: NSResponder <NSApplicationDelegate>
@end

@implementation BoilerplateApplicationController { TestWindowController *windowController; }
- (void)applicationDidFinishLaunching:(NSNotification *)notification { windowController = [[TestWindowController alloc] init]; }
@end

int main(int argc, const char *argv[]) {
  @autoreleasepool {
    BoilerplateApplicationController *controllerDelegate = [[BoilerplateApplicationController alloc] init];
    NSApplication *application = [NSApplication sharedApplication];
    application.delegate = controllerDelegate;
    [application run];
  }
}