You can have Swiss Knife and Oxy Font Manager installed at the same time without any conflict.
Both plugins use the same database tables and what is registered with one will be visible in another as well.
That is done so the user can replace Swiss Knife with Oxy Font Manager once the website is done and he doesn’t need additional features in the production website.
Note: After you remove the Swiss Knife go to:
- Oxygen
- Oxy Font Manager
- Hit the Save button to regenerate CSS