[Destructive Filters?]

In the Affinity Photo Workbook, pg 122, I'm directed to apply a filter via the filter menu: Noise > Add Noise.  I do, it's pretty, but my question is this: Is this a rare example of "destructive" editing, in that for me to change the noise factor I've added would involve going through a series of "undoing"?  That is, there is no way for me to change the parms on the add noise, nor to eliminate it with a click, correct?  This is apparently the nature of filters applied through the filter menu.

[Inpainting tool not functioning]

I select the inpainting brush,  crete a New Layer, and am in that (Pixel) layer.  I paint the area to be removed, see the progress bar telling me it is doing something.  It concludes, the image has not changed.  I can inpaint on the original layer, but not on a new layer, non-destructively.  I have tried right-clicking the layer and selecting "Rasterize".  This doesn't change anything.