Hi Alejandro,
Try something along those lines:
.orbeon .xbl-fr-autocomplete .yui-ac-content { max-width: 600px }
By default the `max-width` is at 400px, hence the above CSS extending it to 600px. Also, you might want to play with the `min-width`, which by default is of 200px, and that you might want to increase as well. And note that the exact CSS to use might depend on what version of Orbeon Forms you're on.
To experiment with this, I'd recommend you use the Chrome Dev Tools, or similar, load your page with the autocomplete, have the list of suggestion show, and then in the DOM look for search for `yui-ac-content` and remove the `display: none` on that element, so the list of suggestions shows while you can experiment with CSS properties in the Dev Tools.
I hope this helps,
Alex
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