Erase invisible area from masking layer

[TLA]

In affinity photo you can rasterize a Layer to erase the image area that lies outside the visible image. How can I delete invisible area of a masking layer in AP ipad?

[MEB]

Hi TLA,
Welcome to Affinity Forums
To rasterise a layer in the iPad versions (Photo/Designer) click the second icon below the header area of the Layers Studio (looks like a few stacked layers) and select Rasterise.