The interesting question here would be : where should you put your note to be able to edit it from either your laptop or phone ?
I can imagine 2 different scenarios :
- You keep your notes on a server, or a cloud, let's simply call it a "remote location". Then both your phone and computer connect to this remote location, not necessarily with the exact same application. You could go this way with Nextcloud and Nextcloud Notes for example, but also Google Keep, Evernote... I would nevertheless recommend to stick with an open file format such as simple txt or markdown to be sure that you'll find an app able to edit your notes.
- You keep your notes on your phone, and you edit them directly on your phone from your computer. You could do this by wired connection, Bluetooth, or even wifi with KDE Connect.
In both cases, there is the note as itself, a file or set of files that is stored somewhere. If you go for proprietary solutions such a Google Keep, you won't even notice the file format. And there is the app to edit the file. Don't focus too much on the app, it doesn't need to be multiplatform if your aim is just to shared notes between devices ;-)
So, per your comment, let me make a suggestion a bit more accurate and arbitrary...
If you don't have one already, you can set up a Nextcloud account at one of the Nextcloud providers (you can click on "Change provider" to see the full list).
Synchronize your Nextcloud on both your phone and PC with the Nextcloud clients.
Then on your phone, you can use the Nextcloud Notes app to edit your notes. That will be your direct icon app.
On your computer, you only have to edit text files in the
<your-synchronized-nextcloud-folder>/Notes path. Any text editor can make it. I like QOwnNotes for this purpose (in your case, you would have to tell QOwnNotes to use
<your-synchronized-nextcloud-folder>/Notes as folder path), but Joplin or even Gedit can make the job too.
I hope this helps :-)