How to make VSCode Intellisense window wider

Another way around this is to press Ctrl + Space (or what ever your "Trigger suggestion" shortcut is) while the suggestion popover is open to show more detail about current selection.

So this (where I can't differentiate between the Trans imported from @lingui/macro and the one from @lingui/react):

Becomes this:

I don't think this is possible, VSCode generally gives extensions very little control over the built-in UI. See also the Restrictions section of the Extensions Capabilities Overview. Technically there is a way to hack around that, but I wouldn't necessarily recommend it.

There are also a number of settings for the suggest widget, but none of them seems to correspond directly to width. The closest you can get would be reducing the font size with "editor.suggestFontSize".