I have a VSCode extension that helps me autocomplete file paths, however many file paths grow long and are truncated in the VSCode intellisense popover window.
How
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".
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: