How to Unerase an Erased area for both the gradient and radial masks?

I'm using the Android mobile version of Lightroom and I love its simplicity but there's one area that really bugs me, and that is the masking tools. Why is it that you can erase a selection of a mask but you can't fill back the areas you've erased? Or am I missing a hidden feature for this?

And whilst I'm here a request to include the color mix pallet/panel in the masks selection would make a lot of sense? - Why would this even be excluded in the first place?

Thanks in advance 🙂