New feature in QGIS 3.12 does not seem to work.
And it looks different from shown in changelog https://qgis.org/en/site/forusers/visualchangelog312/#feature-selective-masking
There is "Symbol layers to mask" part missing, with "This mask shape should be then selected as mask source in the Masks properties of a layer in order to enable masking" instead.
And nothing happened. The label looks exactly the same. So, I oppened up Mask properties again, and found that all check-boxes were unchecked.
What am I doing wrong?