I wouldn’t call it seamless, but I use git with MGit to sync, and Epsilon Notes to view on Android.
I commit and push when I have something new, and pull when I want changes from elsewhere, the same way both on Android and PC. One branch, automatic merging, no lost changes. I would think GitJournal can also do this if set up right.
I’ve used Resilio Sync, Syncthing, FolderSync, Autosync for Google Drive and others for syncing, but specifying which way you want to sync each time seems like an inconvenience that won’t go away.