NSSplityViewの3つのエリアをドラッグ連動してコントロールのサイズを調整します.

//
//  AppDelegate.h
//  Cocoa_splitview_v2

#import <Cocoa/Cocoa.h>

@interface AppDelegate : NSObject <NSApplicationDelegate,NSSplitViewDelegate>

@property (assign) IBOutlet NSWindow *window;

@property (assign) IBOutlet NSSplitView *splitOuter;
@property (assign) IBOutlet NSSplitView *splitInner;
@property (assign) IBOutlet NSTableView *leftTableView;
@property (assign) IBOutlet NSTableView *rightTableView;

@property (assign) IBOutlet NSTextView *textViewConsole;
@property (assign) IBOutlet NSTableView *tableViewProgress;

@end

//
//  AppDelegate.m
//  Cocoa_splitview_v2

#import "AppDelegate.h"

@implementation AppDelegate

- (void) awakeFromNib
{
    NSSize leftTableViewSize = [self.leftTableView frame].size;
    NSLog(@"---left table view: w:%f,h:%f",leftTableViewSize.width,leftTableViewSize.height);
    
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    // Insert code here to initialize your application
}


- (void) splitViewDidResizeSubviews:(NSNotification *)notification
{
    
    NSSplitView *split = [notification object];
    NSString *splitName = [split identifier];
    
//    NSLog(@"split name is %@",[split identifier]);
    
    NSArray *allviews = [split subviews];
    
    if ([splitName isEqualToString:@"split_outer"]) {
        //1.
        NSView *topView = [allviews objectAtIndex:0];
        [[self.textViewConsole enclosingScrollView] setFrame:[topView frame]];
        
        NSView *bottomView = [allviews objectAtIndex:2];
        NSSize bottomSize = [bottomView frame].size;
        NSRect bottomRect = {0,0,bottomSize.width,bottomSize.height};
        [[self.tableViewProgress enclosingScrollView] setFrame:bottomRect];
        
        //2.
        NSView *middleView = [allviews objectAtIndex:1];
        NSRect middleRect = [middleView frame];
        
        NSLog(@"x:%f,y:%f,w:%f,h:%f",middleRect.origin.x,middleRect.origin.y,middleRect.size.width,middleRect.size.height);
        
        //3.                     
        NSPoint point = NSMakePoint(0, 0);
        [self.splitInner setFrameOrigin:point];
        [self.splitInner setFrameSize:middleRect.size];
        
        NSArray *innerSubViews = [self.splitInner subviews];
        
        NSView *leftTableViewOuterView = [innerSubViews objectAtIndex:0];
        NSSize leftTableViewOuterViewSize = [leftTableViewOuterView frame].size;
        [[self.leftTableView enclosingScrollView] setFrameSize:leftTableViewOuterViewSize];
        [[self.leftTableView enclosingScrollView] setFrameOrigin:point];
        
        NSView *rightTableViewOuterView = [innerSubViews objectAtIndex:1];
        NSSize rightTableViewOuterViewSize = [rightTableViewOuterView frame].size;
        [[self.rightTableView enclosingScrollView] setFrameSize:rightTableViewOuterViewSize];
        [[self.rightTableView enclosingScrollView] setFrameOrigin:point];
        
    } else if([splitName isEqualToString:@"split_inner"]){
        NSLog(@"xxxxxxx");//TODO
    }
}

@end