Tachyons?

I missed this before, but so far we have mostly been using Tachyons rather than bespoke CSS classes for styling of this kind (with the exception of this exact file, of course). So instead of popup-menu-text one would write tc pa2 v-top dib as the className (pa1 or pa2, Tachyons intentionally doesn't provide specific pixel offsets for padding so as to keep a consistent, fixed scale). All the other classes either use var or need specific offsets to match a font, so it only applies to popup-menu-text. I will leave to you whether you want to change this, it's not the end of the world if we use classes.

Interesting. Does VS Code itself actually use responsive UI design? Meaning spacing/fontsize/padding change with screen size?

Start by locating the popup-menu-text class and its className usage in the extension UI. Compare that styling with the Tachyons classes discussed in the issue, then confirm whether the intended outcome is to replace this exact class or leave it unchanged. Done means the styling decision is implemented consistently and the relevant UI still matches its existing appearance.