Here are easy steps on how to show hidden apps on Samsung Galaxy A21.
Step 1: Open your phone app menu
Step 2: Tap on the 3 dot icon located beside the search bar at the top right side of the app menu
Step 3: Tap on "Settings" and then scroll down and select "Hide Apps"
Step 4: Now under the Hidden apps category, select the app you want to unhide. You can select multiple apps.
Step 5: After selecting the app, tap on "Done" at the bottom of your screen to apply your changes.
Now that's all. you can still apply these steps to hide any app on your Samsung Galaxy A21.