Last month, Inside Facebook wrote that developers are still clamoring for improved application discovery in the new design, particularly in the Applications menu. Tonight, Facebook told us that it is currently running several A/B tests designed to improve the “discoverability and the usage of bookmarks.”

While Facebook didn’t say exactly what design improvements it is testing, it did say some ideas are minor tweaks while others are more “radical.” Developers will be very interested to see how Facebook improves application discoverability, as many have reported significant decreases in retention due to problematic application navigation in the current version of the site.

Also, in an effort to make it easier for users to edit their settings for recently used applications, Facebook tonight updated the Application Settings page to only show apps used in the last 30 days by default.

“We believe these changes will increase user control over how they interact with apps, and we hope greater control contributes to user willingness to try out application integration points such as auto-publishing stories or adding bookmarks,” Facebook said.

We’ll continue to track all of Facebook’s changes that impact developers and advertisers.