Deleted and moved apps on your Dock way too much and want to bring it to its original state? You can do that, and all it takes is one Terminal command.
Messed up the macOS Dock a Little too Much? Want to Revert Things to How they Were on Day One? You can do that, Thanks to Terminal
Setting up a desktop operating system is always exciting. You start off stock and then push everything to the limit a little too much in order to achieve the look and feel which suits you best.
If you've been using a Mac for a long time, you probably started off your customization journey by moving things around in the Dock that sits at the bottom of the screen. If you don't use the stock Apple apps at all, then those were the first ones to go and you probably changed things around a little too much, including the settings related to how app icons are animated when you click on an icon and so on. That's perfectly normal until you come to a point where you are required to reset the Dock to its original state, for whatever reason.
Sure, you can factory reset the entire Mac - that's one option, and definitely not the brightest one. But, what if you don't have to do that at all, and instead revert to the stock Dock apps arrangement and settings with a simple Terminal command instead? Well yes, you can do that as well.
Tutorial
Step 1. First of all, launch Terminal. Just bring up Spotlight search (Command+Space) and type in Terminal and hit the Return key.
Step 2. Copy the following command, paste it in Terminal and hit the Return key:
defaults delete com.apple.dock; killall Dock
Step 3. The Dock will now immediately return to the state how it was when you first booted up your Mac.
At this point, you can either start customizing things up again, or if you're just planning to give the Mac to someone else, then leave things as they are. Just make sure you sign out of your Apple ID while doing so, if you’re going for the latter option.
I really wish there was a simple setting inside macOS that would just let you reset the Dock completely. Instead, we get a Terminal command which most users will never ever know about. But hey, if you found out about this command, why not share the secret with everyone else out there too?
source https://wccftech.com/how-to/reset-macos-dock-to-original-apps-arrangement-and-settings-tutorial/