Here is how LSHandlerRank key looks like in the info.plist.
OR (Open info.plist as 'Source Code' & add)
<key>CFBundleDocumentTypes</key>
<array>
<dict>
<key>CFBundleTypeIconFiles</key>
<array/>
<key>CFBundleTypeName</key>
<string>Text</string>
<key>LSHandlerRank</key> //Key you need to fix your issue //
<string>Alternate</string> //Here value can be Owner, Default or Alternate
<key>LSItemContentTypes</key>
<array>
<string>public.plain-text</string>
</array>
</dict>
</array>
Here is the description from Apple why and how you can provide the LSHandlerRank Key.
Determines how Launch Services ranks this app among the apps that declare themselves editors or viewers of files of this type.
The possible values are:
Owner (this app is the primary creator of files of this type),
Default (this app is an opener of files of this type; this value is also used if no rank is specified),
Alternate (this app is a secondary viewer of files of this type), and None (this app is never selected to open files of this type, but it accepts drops of files of this type).
Launch Services uses the value of LSHandlerRank to determine the app to use to open files of this type.
The order of precedence is: Owner, Default, Alternate. This key is available in macOS 10.5 and later and iOS 3.0 and later.
You can find more on this link: https://developer.apple.com/documentation/uikit/view_controllers/adding_a_document_browser_to_your_app/setting_up_a_document_browser_app