Grant external apps permission to write to a file created by my app

Question

I am trying to achieve the following in a Blazor Hybrid app for android, written in c# in VisualStudio 2022:

1. make my app create and store a text file with some basis content (works)
2. launch (using Launcher.Default.OpenAsync) or share (using Share.RequestAsync) the file, allowing the user to select an app to modify the text file
3. allow the user to save the file in the same location as where my app put it

At step 2: When prompted, I choose QuickEdit. Launcher works as expected: my text file opens. Share fails, however: QuickEdit opens an empty file.

It fails at step 3: I get writing permission denied messages, with the suggestion to export the FileProvider (which is not possible: build fails if I try) or getUriPermission (which I tried to set)

Does anyone know how to do this in a Blazor Hybrid app?

Update

Trying to implement @blackapps comment, I changed my code to this:

var fn =  "nieuw.txt";
var docsDirectory = Android.App.Application.Context.GetExternalFilesDir(null);
var file = Path.Combine($"{docsDirectory.AbsoluteFile.Path}", fn);
var myUri = Android.Net.Uri.Parse(file);
fileExists =  File.Exists(file).ToString();
Android.Content.Intent viewDoc = new Android.Content.Intent(Android.Content.Intent.ActionView);
viewDoc.SetDataAndType(myUri,"text/plain");
viewDoc.SetFlags(Android.Content.ActivityFlags.NewTask);
viewDoc.AddFlags(Android.Content.ActivityFlags.GrantReadUriPermission);
viewDoc.AddFlags(Android.Content.ActivityFlags.GrantWriteUriPermission);
Android.App.Application.Context.StartActivity(viewDoc);
message = myUri.ToString();

I am prompted to choose an app (which is as intended) but the app opens an empty text file.

This, however, does work, but I can't save (in the same location) as explained before.

string popoverTitle = "Read text file";
var fn =  "nieuw.txt";
var docsDirectory = Android.App.Application.Context.GetExternalFilesDir(null);
var file = Path.Combine($"{docsDirectory.AbsoluteFile.Path}", fn);
await Launcher.Default.OpenAsync(new OpenFileRequest(popoverTitle, new ReadOnlyFile(file)));

Any suggestions?