To create a custom theme:
- Open the menu by clicking either the grey button or your picture at the top right of the page.
- Open the settings dialog by selecting the Settings option in the menu.
- Click Background under Visual in the navigation menu on the left.
- Click the Select a theme button.
- In the dialog that opens, click the blue Create a theme button at the bottom left.
- Enter a name and configure any other options until the preview looks the way you'd like your theme to.
- When you're done click the blue Save & Close button to save your theme.
- Mouse over the theme in the list and click either Use to install it or Preview to see what it'll look like.
- Click the blue Save & Close button at the top right of the main settings dialog to exit the settings.