Welcome to the forums!

There's no such option in default installation. Although you can do this with a very simple plugin.

I'll help you create a plugin if you want to.

Thank you for your responding!

I would very much appreciate help with the plugin yes, I will start reading through this area of the documentation in the meantime but any tips and guidance is welcome :)

You can get some ideas about how plugins work reading comments in plugins/test_plugin/
And you can start creating your own playing with plugins/skeleton.plugin.php

Basically your future plugin should include at least these 2 events

// This event will call the next one by creating a dummy "content" request
function AdminAfterMenuInit()
{
	global $ctrl, $action;
	
	if( $ctrl == 'items' && $action == 'new' )
	{	// Dummy content, don't remove
		$GLOBALS['content'] = ' ';
	}
}



function FilterItemContents( & $params )
{
	global $Blog;
	
	// Get the main category
	$main_category = param( 'post_category', 'integer', $Blog->get_default_cat_ID() );
	
	$template = ''; // Default template, overwritten below
	
	if( empty($main_category) )
	{	// No category selected, use a common template
		$template = 'No category selected';
	}
	else
	{	// A category is selected,
		// let's get a template for specific category ID
		switch( $main_category )
		{
			case 4: // Category #4
				$template = 'You selected category #4';
				break;
			
			case 22:
				$template = 'Category #22, not a bad choice';
				break;
			
			default: // Some other category selected
				$template = 'Some other category selected';
		}
	}
	// Set our template
	$params['content'] = $template;

	return true;
}