Samsung
Remove Apps from Secure Folder auf Samsung
Every app you add to Samsung Secure Folder gets installed a second time inside an isolated Knox container. That is why uninstalling it from inside the folder never affects the version running on your normal home screen, you are only deleting the container copy.
The confusion usually starts with the gesture itself. Tapping and holding the app icon inside Secure Folder opens a short menu that looks similar to the regular app switcher, but the Uninstall option here only targets the sandboxed copy and any data saved inside it.
How to remove an app from Secure Folder
Open Secure Folder, then tap and hold an App you want to remove. Tap Uninstall in the menu that appears, then confirm with OK. The app disappears from the folder immediately, while the original app outside stays untouched with its own data intact.
If you only want to hide an app from Secure Folder without losing its data, moving it back to the regular home screen is a better option than uninstalling, since that keeps the container copy and its settings. Uninstalling is the right call once you no longer need a separate, isolated instance of that app at all.
Deleting removes any data stored inside that sandboxed instance permanently, so back up anything important before you confirm.