The new `getrpcinfo` shows a list of the active commands and the duration each command has been running. This sounds like a good place to report a completion percentage for any command doing a blockchain rescan, to solve [this problem](https://bitcoin.stackexchange.com/q/83236/90721).
{
    for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++)
        handlers.emplace_back(chain.handleRpc(commands[vcidx]));
}