After a long long time, I added another button to my apps dialog. I had localized strings implemented. So I found a similar one like
/* Class = "NSButtonCell"; title = "Keep number"; ObjectID = "2yE-rM-5Sn"; */
"2yE-rM-5Sn.title" = "Nicht umnumerieren";
in file "Main.strings (German)". Unfortunately I forget, how I got there. I did the entire translation in one step in one night. Now I only need to get one new translation for the newly added button. Any hint how to do this?