They hid the Feature suggestion forum and, unfortunately, I can't provide a link in the Ask a Question forum...
1. Sign in on windowsphone dot com (preferably on a PC where it's easier to see everything)
2. Click on How-To (top menu bar).
3. Below the top section, you'll see a column of icons with the heading "Spotlight." Click on the second one, "Support and Troubleshooting" (the blue wrench).
4. The last question in the "Choose a Category" section (directly below the picture) is "Where can I submit Windows Phone Feature suggestions?"
I highly recommend searching to see if there is already a post for that feature that has the support of other users. The search box is not where it should be. Look in the lower right column for it.