Thank you for using Apple Support Communities. It's my understanding that the Dock on your MacBook intermittently becomes frozen and highlights apps. I'm happy to help.
Try testing this issue in safe mode. Starting in safe mode allows your Mac to run certain checks, remove caches, and prevent login items from automatically launching. This can isolate possible third party issues. Use the steps and information in the link below for assistance with safe mode:
Use safe mode to isolate issues with your Mac
If the issue persists, test in another user account. This will help determine if the issue is user specific or system wide.
How to test an issue in another user account on your Mac
Please let us know the results. Include any additional troubleshooting steps you may have tried.
Have a wonderful day!
Oct 14, 2017 12:38 PM
Would you like to add frequently used applications or documents to your Dock? Would you like to remove rarely used items from the Dock? If so, below are instructions on how to do this. The Dock is the row of icons that’s typically located across the bottom of the screen, though it can be moved. Apple populates the Dock with items that they think, or want, you to use, but you can customize it to suit your own needs. You can add applications, documents or folders to the dock.
Dock Basics
Hide recent apps in Dock. The new recent-apps section is smart enough that it shows only recent apps that aren't already in your Dock. It can be helpful to return quickly to an app you recently. Oct 22, 2018 The Dock in MacOS Mojave includes a new feature that displays a trio of recently used applications alongside your regular Dock app icons. The Recent Applications section of the Dock adjusts and updates automatically as you launch and quit apps, and while it offers a convenient way to reopen apps you were using not long ago, some users may prefer to not have the feature enabled for whatever.
- The Dock is divided into two, disproportionately sized sections. Look for the dividing line which appears a little bit to the left of the Trash. The left-hand section can contain Application icons. The right-hand section can contain icons for files, folders or web sites.
- When you’ve opened an application on your Mac you’ll see its Dock icon displays a small black dot below it. (Older versions of the Mac operating system displayed either white horizontal bar or a bluefish white circle, both of which are hard to see, if you ask me.)
- Apple populates the Dock with some of its applications. You can rearrange or remove these icons using the instructions below.
- When you open an Application whose icon is not already on the Dock, this application’s icon will temporarily appear on the Dock. When the application is quit its icon will vanish from the Dock.
- The Finder icon, which appears at the far-left end, and the Trash icon, which appears at the the far right-end, can not be moved around or removed. They are locked in place.
- Clicking and holding an icon on the Dock produces a menu of choices. For example, if you click and hold on the Trash icon its menu lets you choose to either open the trash or empty it (if you have files in the trash).
Rearrange Items On The Dock
- To rearrange icons on the Dock, click and drag an icon to either the left or right.
Remove Items From The Dock
- Click and hold on a dock icon to display its menu.
- Select Options
- Select Remove From Dock (If you want to remove a Folder icon, hold down the Control key and then click and hold its icon to see it’s menu.)
Mac Stop Apps From Staying In Dock
Add Applications To The Dock
- There are a few ways to add Applications to the Dock but this one is the one I use most often.
- Click on the Finder icon on the Dock to open a Finder window
- Click on the Go menu, at the top of the screen, select Applications.
- Locate the application that you want to add to the Dock.
- Click and drag this application’s icon to the left-hand section of the Dock. (Make sure you don’t drag this icon on top of another dock icon. Instead, make sure that you see the dock icons scoot to the side to make room for this new icon.)
Add Files or Folders To The Dock
- Click on the Finder icon on the Dock to open a Finder window
- Navigate to the file or folder that you want to add
- Click and drag this application’s icon to the right-hand section of the Dock (Make sure you don’t drag this icon on top of another dock icon. Instead, make sure that you see the dock icons scoot to the side to make room for this new icon.)
Change The Dock’s Location
Mac Prevent Apps From Staying In Dock Free
- Click on the Apple menu and select System Preferences
- Click on the Dock icon
- Locate the Position on screen section and select, Left, Bottom or Right.
Mac Prevent Apps From Staying In Dock 2017
You might also be interested in Apple’s Dock overview article.