Hey @muskanb,
Freshdesk standard theme doesn’t offer dark-mode theme option. You would need to customize your theme file via CSS/Javascript route. There are some available Javascript libraries to implement this. I’m not sure if Freshdesk is going to add this feature in their next iteration of the Marina theme.
With regard to font/spacing customization, this can be done when you use the HTML editor mode while editing an article:

You can add custom HTML tags and CSS styles to change the font. For instance, you can use the <span> tag with CSS styles to change the font style. Here's an example: <span style="font-family: Arial;">Your text here</span>.
Adjusting the spacing between lines or paragraphs in support articles is also possible. You can achieve this by using CSS. To adjust the line spacing (leading), you can use the line-height CSS property. To adjust the spacing between paragraphs, you can use the margin CSS property. Here’s an example : <span style="line-height: 1.5;">Your text here</span>
Hope this helps!
We definately need a dark mode please ??
Shouldn’t be a big ask ??
any update on that front FreshWorks team please ?