Would it be possible to add an option to specify the amount you want to invest when purchasing fractional shares, so the quantity would be calculated automatically for you?
For example, if you want to invest 100 EUR, you would click a (new) button where you could enter 100.00, then the app would calculate the maximum number of shares that can be purchased for up to that amount and fill that value in the quantity field.
Now, you have to manually calculate the number of shares you can purchase for a set amount, which is tedious if you are spreading your investment on a wide range of instruments. My current portfolio has 64 shares and will be growing, thanks to your fractional shares.