The following snippets assume you are using a PTDocumentController called documentController:

PTDocumentController documentController = new PTDocumentController();

documentController.ToolGroupIndicatorView.Hidden = true;

The toolbar can be programmatically hidden by setting the mode to view group, which is a special group and the only group where the toolbar is hidden:

documentController.ToolGroupManager.SelectedGroup = documentController.ToolGroupManager.ViewItemGroup;

The toolbar can be shown again by changing the group to any group other than view:

documentController.ToolGroupManager.SelectedGroup = documentController.ToolGroupManager.DrawItemGroup;

Toolbars can be removed by removing them from the toolGroupManager's groups array. The following code removes the "Draw" and "Pens" toolbars:

NSMutableArray<PTToolGroup> mutableGroups = new NSMutableArray<PTToolGroup>(documentController.ToolGroupManager.Groups);

mutableGroups.RemoveObject((nint)mutableGroups.IndexOf(documentController.ToolGroupManager.DrawItemGroup));
mutableGroups.RemoveObject((nint)mutableGroups.IndexOf(documentController.ToolGroupManager.PensItemGroup));

documentController.ToolGroupManager.Groups = NSArray.FromArray<PTToolGroup>(mutableGroups);

The example below shows how to remove the text highlight and text underline button from a toolbar.

PTToolGroup annotateGroup = documentController.ToolGroupManager.AnnotateItemGroup;

// tool buttons that exist currently
UIBarButtonItem[] defaultAnnotateGroupTools = annotateGroup.BarButtonItems;

// new set of tools to replace current ones
NSMutableArray<UIBarButtonItem> newAnnotateGroupTools = new NSMutableArray<UIBarButtonItem>();

// add all currently existing tools except for the ones we don't want
foreach (UIBarButtonItem defaultToolItem in defaultAnnotateGroupTools) {
    if (defaultToolItem.IsKindOfClass(new ObjCRuntime.Class(typeof(PTToolBarButtonItem))))
    {
        PTToolBarButtonItem toolBarButton = (PTToolBarButtonItem)defaultToolItem;

        if (toolBarButton.ToolClass.Equals(new ObjCRuntime.Class(typeof(PTTextHighlightCreate))) ||
                toolBarButton.ToolClass.Equals(new ObjCRuntime.Class(typeof(PTTextUnderlineCreate)))) {
            continue;
        }
        else {
            newAnnotateGroupTools.Add(defaultToolItem);
        }
    }
    else {
        newAnnotateGroupTools.Add(defaultToolItem);
    }
}

// assign tools to new array
documentController.ToolGroupManager.AnnotateItemGroup.BarButtonItems = NSArray.FromArray<UIBarButtonItem>(newAnnotateGroupTools);

// create a mutable array of the current items in the annotation toolbar group
NSMutableArray<UIBarButtonItem> availableTools = new NSMutableArray<UIBarButtonItem>(documentController.ToolGroupManager.AnnotateItemGroup.BarButtonItems);

// create a new toolbar item for freehand annotations
UIBarButtonItem[] freeHandItem = { documentController.ToolGroupManager.CreateItemForToolClass(new ObjCRuntime.Class(typeof(PTFreeHandCreate))) };


// add the freehand annotation item to the front of the list
availableTools.InsertObjects(freeHandItem, new NSIndexSet(0));

// assign the array back to the annotation toolbar group.
documentController.ToolGroupManager.AnnotateItemGroup.BarButtonItems = NSArray.FromArray<UIBarButtonItem>(availableTools);

The code below creates a new toolbar that contains a free hand, cloudy and image stamp tool.

UIImage image = new UIImage("square.and.pencil");

// the tools it will contain
UIBarButtonItem freeHandItem = documentController.ToolGroupManager.CreateItemForToolClass(new ObjCRuntime.Class(typeof(PTFreeHandCreate)));
UIBarButtonItem cloudyItem = documentController.ToolGroupManager.CreateItemForToolClass(new ObjCRuntime.Class(typeof(PTCloudCreate)));
UIBarButtonItem stampItem = documentController.ToolGroupManager.CreateItemForToolClass(new ObjCRuntime.Class(typeof(PTImageStampCreate)));

UIBarButtonItem[] tools = { freeHandItem, cloudyItem, stampItem };

// the name of the custom group, its image, and its tool items
PTToolGroup customGroup = PTToolGroup.GroupWithTitle("MyApps Group", image, tools);
            
NSMutableArray<PTToolGroup> groups = new NSMutableArray<PTToolGroup>(documentController.ToolGroupManager.Groups);
groupss.Add(customGroup);

// add the tool group
documentController.ToolGroupManager.Groups = NSArray.FromArray<PTToolGroup>(groups);

Your app may need a button that does not invoke one of the built in annotation tools. The following code will add a button that calls a selector.

PTSelectableBarButtonItem selectableItem = new PTSelectableBarButtonItem();
selectableItem.Title = "Custom Tool";
selectableItem.Image = UIImage("square.and.pencil");
selectableItem.Style = UIBarButtonItemStyle.Plain;

NSMutableArray<UIBarButtonItem> availableTools = new NSMutableArray<UIBarButtonItem>(documentController.ToolGroupManager.AnnotateItemGroup.BarButtonItems);

availableTools.Add(items);

documentController.ToolGroupManager.AnnotateItemGroup.BarButtonItems = NSArray.FromArray<UIBarButtonItem>(availableTools);

If you want to toggle the items selection, flip its selected property:

selectableItem.Clicked += (button, e) => { 
    button.isSelected = !button.isSelected
}

You can modify the navigation bar items. Here is an example of adding a new button (for the current size class):

UIBarButtonItem myItem = new UIBarButtonItem(UIImage("square.and.pencil"), UIBarButtonItemStyle.Plain, null);

NSMutableArray<UIBarButtonItem> navigationItems = new NSMutableArray<UIBarButtonItem>(documentController.NavigationItem.RightBarButtonItems);
navigationItems.Add(myItem);
             
documentController.NavigationItem.RightBarButtonItems = NSArray.FromArray<UIBarButtonItem>(navigationItems);

Tools can also be added:

UIBarButtonItem freeHand = documentController.ToolGroupManager.CreateItemForToolClass(new ObjCRuntime.Class(typeof(PTFreeHandCreate)));
NSMutableArray<UIBarButtonItem> navigationItems = new NSMutableArray<UIBarButtonItem>(documentController.NavigationItem.RightBarButtonItems);
navigationItems.Add(freeHand);

documentController.NavigationItem.RightBarButtonItems = NSArray.FromArray<UIBarButtonItem>(navigationItems);

Note that in the example above, de-selecting the tool button item needs to be implemented by the app, by listening to the Tool Did Change notification.

These are the buttons that appear at the bottom of the screen.

// new button
UIBarButtonItem myItem = new UIBarButtonItem(UIImage("square.and.pencil"), UIBarButtonItemStyle.Plain, null, null);

// spacer to keep evenly spaced buttons
UIBarButtonItem spacer = new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace, null, null);

// new array
NSMutableArray<UIBarButtonItem> toolbarItems = new NSMutableArray<UIBarButtonItem>(documentController.ToolbarItems);
toolbarItems.Add(spacer);
toolbarItems.Add(myItem);

// set the toolbarItems to the new items
documentController.ToolbarItems = NSArray.FromArray<UIBarButtonItem>(toolbarItems);