OK, I did get my hands dirty. Followed the instructions in this thread and created a new layout for the thumb keyboard that has the following changes:

Lower case, first tab: Key for ".,? " etc. is now smaller, additional space used for letter ß.

Second tab: Letter ß replaced by "…" - I often use this and find it very difficult to type as three "."s because you'd need to pause for ~1sec after each tap in order not to get "," or "?" after the first tap.

"Shift" is not very comfortable the way it is, but as things are, I'll not get used to the thumb keyboard any time soon and probably end my experiment to return to the regular stylus-VKB, anyway.