Introduction
Here is a quick end to end build of a solution for adding navigation to your PowerApps using the Gallery control and a Collection.
Use Case
If you have an app with multiple pages within it, managing the navigation can be difficult - you end up repeating work on each page.
Overview
Here’s a quick rundown of the solution:
Create a collection to store the navigation’s labels and screens.
Use a Gallery to display the collections values and perform the navigation
Use Global Variable to keep track of what has been selected
We tried to keep it as simple as possible: Two controls and a Collection
Build
Step 1: Create a Collection
Assuming you’ve already created the pages for your app, you can load a Collection with the values for your PowerApps navigation. I suggest binding it to your PowerApp’s OnStart event.
NOTE: Screen1 (below) is a reference to the name of a screen in your app that you’d like to navigate to.
ClearCollect(collAppNav, {title:"Nav 1", screen:Screen1}, {title:"Nav 2", screen:screenHazards},{title:"Nav 3", screen:Screen2} )

Build your navigation collection when the app starts
Step 2: Build Your Gallery
Add a Gallery Control to your PowerApp’s screen
Set the Gallery’s Items property to:
collAppNav
Step 3: Add a Button to your Gallery template
Add a Button to the Gallery template
Set the Button’s Text property to:
ThisItem.title
Set the Button’s OnSelect to:
Set(currNav,ThisItem.title);Navigate(ThisItem.screen, Transition.None)
This sets a variable that keeps track of the currently selected screen and navigates you to the next screen
Create a gallery of buttons.
Step 4: Style the Button
Set the Button’s Underline property to
If(currNav = ThisItem.title, true, false)
Step 5: Copy and Paste the Gallery
Copy and Paste the Gallery onto the other screens in your app.
Conclusion
Nothing too fancy here! Quick and easy navigation for your next PowerApp.