Tap'n'hold on any key. Then either just tap on a character in the popover or hit "edit" and add new characters.

I would prefer if the alternative actions that pop up when holding the buttons were individually configurable.

We currently have two groups: Left. Right. The idea being that one might want start/end stuff like (abc), **abc** separated from single character inserts, such as *, # etc.

This already poses some problems when trying to "move" a character from the left side to the right, and I can only imagine it getting even more confusing if every button had its own set of alternate chars. For one, you'd need to setup every button, and you might loose chars if you dleted a button…

But maybe I misunderstood your request. :)

Hm. You'd need to remember which alternative characters sit beneath which key. We'll think about it, as it would greatly enhance the number of alternative characters quickly available, but don't count on it. :)

But why would you need Ä, Ö etc in the keyboard row? Why not use a German keyboard layout?
(in case you don't know, you add keyboards in the global prefs)

On the German iPad keyboard, you can also just swipe up on a/o/u/s to get ä/ö/ü/ß, same for capital letters. This takes about the same time as just typing a/o/u/s and less time than moving your finger to the additional keyboard row. Took me a while to notice that, but now I always try the same on regular keyboards ;)

If you still want to have ä/ö/ü/ß on the additional keyboard row, you can simply modify the keys: Tap and hold any of the additional keys, then choose New, then enter the desired letter as Start, save (Done), then select it from the list to apply it for the currently selected button. Use the + buttons in the middle of the keyboard row to add more buttons.

And about navigation buttons: Try tapping in the margins to the left and right of the text with one or two fingers – in my opinion a much better way to navigate through the text than buttons :)

To select any of the given symbols, you need to tap the arrow. If you don't do that but tap inside the blank area to the left of the arrow, entering anything should work.

I'd like to suggest that one of those initial files should contain this information on how to configure those symbols and also explaining the function of the right and the left group of chars. I thought it was not possible to edit those keys until I found this post and I was almost giving up using daedalus because I could not configure the keys to better support markdown editing.