One feature that would be very helpful is the ability to preview the ADIF file before exporting it. Being able to examine the entire ADIF file in a single grid-style, scrollable view would allow an activator to ensure each QSO logged has the correct information in it.
As the app introduces the ability to enter my county, state, and grid square, in addition to my park number, being able to check the full log for errors would be extremely valuable. This is especially important since the app allows these fields to be different for every single QSO in the same log.
A friend started entering QSOs and forgot to enter his park number until partway through the activation. He only caught it by exporting the ADIF and reading it with ADIF Master on a Windows PC. An ADIF export preview would catch errors like this.
On a related note, I still prefer the ability to mark some things as “applies to entire log” to avoid these types of errors. My park, county, state, and grid square aren’t going to change during a typical activation, so checking these as “static” or “whole log” (as a user option) would help to avoid such errors. Likewise, if I realize I had inadvertently entered the wrong Grid square or park number for my activation, I could change it once and apply it to the entire log instead of editing each and every QSO.