Notepad++ permanent line marking?

Solution 1:

They offer a line marking (blue dots in the picture below), but I can't save the marked state.

The "blue dots" are called bookmarks.

To save the bookmarks you need to enable sessions.

To enable sessions:

• menu Settings → Preferences
• select Backup
• enable Remember current session for next launch

Notepad++ doesn't even give me the option to save when I add bookmarks.

Use menu File → Save Session...

Changes not automatically saved

Here are a few ways changes may not get saved to the session file.

• If you change bookmarks or folded lines via the menu or a keyboard shortcut then terminate Notepad++ without doing anything that would cause the session to be saved. This is because a plugin cannot detect those events. Clicking in the bookmark or fold margins is detected.
• If you close a file then immediately terminate Notepad++ (see sessionSaveDelay in Manual Settings).

• If you do anything that results in a change to one of the following then immediately terminate Notepad++ (see settingsSavePoll in Manual Settings).

  • bookmarks
  • folded lines
  • filters
  • favorites
  • sort order
  • dialog window sizes
  • default session name

Source Session Manager help