Quick and dirty.
Admin → Customize → Themes → Edit CSS/HTML → Common tab → Head tab:
Set additional tags:
<meta name="theme-color" content="#ff0000">
<meta property="og:description" content="Whatever you want">
The tags will be duplicated in the HTML code, but what you want to achieve will work.
Here’s an example where I replaced a black line with a red one and set “Texte arbitraire” in the og:description tag:
A better solution would be to actually replace the value instead of duplicating tag, but I don’t know how to do that.