I think it would be great if you could sort the individual holdings in the holdings tab of the pie not only by weight, target weight or name but also by gains / losses percentages.
Also I would like to see selectable time frames like in this example from another broker:
You already have similar functionality in the portfolio overview, but not inside the individual pies.
The sorting functionality could also be applied to other pages which seem to be lacking basic functionality. For example the watchlist, which is not sortable by daily gains or similar even in the advanced view on a desktop device.
Edit: Also when exporting investments from a pie, there is no way to differentiate two holdings under the same name as in this example with Kongsberg and Saab:
Which is the one in EUR and which is the one in USD? Maybe just add a small currency symbol next to the Icon?