Text wrapping is not possible. It would make the TOC much longer as well, wondering if that is a good choice. You can however change the font size and the width of the TOC using the Settings. Did you look at them:

In this screenshot I increased the width of the TOC from 250 to 300px. For the Level 1 settings (those are your slide titles, if you use groups you'll have to change the Level 2 settings) I decreased the font size from the default 12pt to 9pt.
Moreover are you aware that editing the text is possible as well? You don't have to keep the slide names (I would never use spaces in slide names or in any name BTW, but that is another discussion), you can double-click and change the text. Do that only as a last action, not when you still have to use the button to refresh TOC settings.