The only things I can edit if presets were already created are their existence (delete) or order. All other advertised aspects like volume or EQ are not present.
I have WiiM Mini but nowhere in manuals of WiiM Mini, WiiM App or WiiM Remote I could find a mention that presets capabilities are restricted there.
And why would such a restriction exist even? How much space you would need on the device to save information such as volume or eq levels? 1kB?