Setup in Lightning Experience:
The navigation bar in Lightning Experience provides an efficient and consistent interface to navigate through our organization’s various apps and items. Similar to Salesforce Classic, apps in Lightning Experience give our users access to sets of objects, tabs, and other items all in one convenient bundle in the navigation bar. However, apps in Lightning Experience take things to another level beyond apps in Salesforce Classic by letting we brand our apps with a custom color and logo.
Disable personalize the navigation bar for a specific app:
Step-1: Go to the Setup and Type apps. Select the ‘App Manager’ in the below option.
Step-2 : Now In App Manager, Choose any one of the app and Click ‘Edit’
Step–3 : Then inside the App Setting, Click the ‘App Options’
Step-4 : Then Select the option Disable end user personalization of nav items in this app in the ‘App Personalization Setting’ and click the Save.
Disable personalize the navigation bar for a any app:
Step-1 : Go to the Setup and Type ‘user interface‘.
Step-2 : Then Choose the ‘User Interface’ from the setup.
Step-3 : Now choose the feature ‘Disable Navigation Bar Personalization in Lightning Experience’ from the ‘User Interface’.
For reference : Click Here
For More : Click Here