When applying an Effect to a Mask, for example, a Gradient Fill, the mask thumbnail remains white and does not show an effect is present.
I can get the mask to show using this procedure
1. Add mask to an image layer
2. Add Gradient Fill effect to mask
3. Click Refine Mask
4. Click Apply
Then the mask thumbnail shows the gradient.
Mask Thumbnail Does Not Show Effects Applied
2022-08-03 11:01:36
Or use an Effects: Gradient filled rectangle as a mask:
2022-08-03 12:06:21
Drag the Rectangle with the Arrange tool (V) onto the image which gets highlighted and hold additional cmd key till its icon is turning into a mask icon - release. Then add Effect->Gradient fill to still selected Rectangle (now Mask) and adjust accordingly.