I copy and paste an entry the number of times needed, but it’s tedious to have to touch each line and replace the number with the next one. There’s got to be an easy recipe for replacing multiple selections with an incrementing value.
in cases where I’ve needed the selection to start from 0, I use <a-s-)> to rotate the selections forward after the replacement, then just replace the first value with a 0 manually. There’s probably a better way, though!
After pasting the selection index with <c-r># you can write -1 in the buffer and pipe to bc to make them start from zero. Make sure the 1-1, 2-1, 3-1 and so on are selected and use |bc<ret>.