Adobe released the 12.1 update to Lightroom Classic in December 2022. Most of the updates apply to the Masks panel, which has a different layout and some extra functionality.
You can see the difference between the old layout and the new one in the screenshots below.

Here’s a summary of the changes.
1. The sliders are now arranged into four groups – Tone, Color, Presence and Detail.
2. You can click the triangle next to a group name to hide or reveal the sliders in that group.

3. Right-clicking on the Masks panel brings up a menu. One of the options is Solo Mode.

Click on this and Lightroom opens up one slider group at a time. You can see the difference below.

4. Each slider group has an eye icon that you click to hide or reveal the effects of the sliders in that group. It’s grayed out if you haven’t adjusted any of the sliders.

The eye icon is useful when you’re in Solo Mode or some of the groups are closed. When the eye icon is lit up, it shows that you’ve adjusted at least one slider in that group. If it’s black, it means that you haven’t adjusted any of the sliders.

5. The Reset Sliders Automatically checkbox has moved to the top of the panel.
6. There are new Delete Empty Mask and Delete All Empty Masks options in the menu that appears when you click the three dot icon next to any mask.
Note that you’ll only see this option if your photo contains empty masks.
This is useful if you apply an adaptive Develop Preset, sync photos that have AI masks or copy and paste masks from one photo to another.
For example, you might copy and paste a Teeth mask from a portrait where you can see somebody’s teeth to another where you can’t. In the second portrait the Teeth mask is empty (because there are no teeth for Lightroom to mask). You can delete it quickly (along with any other empty masks) using the Delete All Empty Masks option.


Mastering Lightroom Classic: Book Two – The Develop Module
You can learn more about masking and the Masks panel in Lightroom Classic with my ebook Mastering Lightroom Classic: Book Two – The Develop Module