I have a newer Samsung tablet with attached keyboard. During POTA, I would receive (and type out) the suffix of the callsign and ask what their prefix was. When I’d arrow back to the beginning, I could type the first letter of their call and then the cursor would return me to the end of the field.
So for instance, if I heard “ABC” and missed their prefix “KB0”, I’d type:
Then arrow to the right and it would put in the “K”. But then the cursor would go to the end where I’d add in the “B0”. I’d end up with a callsign that looked like: