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My initial thought based on the information you've given is update bugs sometimes need to have a cache cleared somewhere. Many times a simple cache clear clears things up, pun intended.
App Cache
Settings>Applications>(the name of your notes app)>Storage>Clear Cache/Clear Data. You shouldn't lose anything clearing the cache, you might lose something clearing the data for this app. If it stores items in the cloud more than likely clearing the app data will only cause you log back in to your account.
Partition Cache
Power off the device>hold the power button and the volume up button until the splash screen appears and then release the power button only>hold the volume button until the phone is fully booted to the bootloader/recovery screen>use the volume buttons to navigate and the power button to select and choose Wipe Partition Cache>after complete choose the reboot option and allow the phone to reboot normally.
If neither of those worked for you, I plugged your question into Google and found the response below, which doesn't sound promising. Your best bet would be to contact the developer. They may have a work around, know of someway to accomplish this and if nothing else they'll have some feedback. Honestly, without a specific setting, we're not likely to have much advice for you for this problem.
This is what Google says.
There is no specific setting within the app or system settings to change the default landing tab of the OnePlus Notes app from "To Do" back to "Notes". This behavior appears to be an unchangeable default in your specific app version (12.5.18_13da978_220427).
However, you can try some workarounds or troubleshooting steps that community members have used for similar app issues:
- Force Stop and Clear Cache: This might reset the app's current session or temporary preferences.
- Go to your phone's Settings menu.
- Tap on Apps, then select Notes (or go to App Management/Details).
- Tap on Storage & cache.
- Tap Clear cache.
- Go back to the previous screen and tap Force stop.
- Restart your phone and open the Notes app again to see if the default has changed.
- Use the Shortcut: You already know this, but holding down the app icon for a few seconds should bring up an option to jump straight to a new note, which bypasses the main app screen.
- Check for an App Update: The issue might be a bug that a newer version has fixed. The app updates are delivered via system updates (SOTA) directly from OnePlus, not always via the Play Store.
- You can check for system updates in your phone's main settings under System or About device.
- Alternatively, you can visit the OnePlus Community forum and search for the latest information or bug reports regarding the Notes app.
- Consider an Alternative App: Many users on the OnePlus forums recommend using a different, more reliable notes application like Google Keep or ColorNote, which offer better cross-platform support and cloud backup.
If none of these steps work, the behavior is likely intended for that specific app version. You can officially report this as a bug or provide feedback on the OnePlus community forum to let the developers know this is a desired feature.
Look for Developer contact information either on the app's page in the Play Store or in the contact section of the app settings. Let them know your issue and see if they respond.
Best wishes.