1) Did you put a few lines of code into the program code, which is responsible for the address book? because this is only a few lines - but so much convenience for all clients of the network

2) Is there protection against the fact that the computer accidentally turns off when the purse is running ... and again shakes the whole blockchain from the very beginning because of the damaged database? because the database is one file ...
Or is there still no partitioning of the database into multiple files or is there no protection against the failure?

you are inattentive, you did not read all messages in this thread recent
there is a big problem in sending coins from one exchange to another directly ... I do not know what it is connected with, but the developers strongly advised first to withdraw coins from one exchange to their own purse, and only then from their wallet to transfer coins on the second new exchange