They said the rule will look something like this
<Rule action="block" enabled="1" action_id="0" hostnames="domain1
domain3
domain4
domain5
domainX" name="Block Domains" />
I created block rules by adding 5 domains using the program first then opened the config file and added many more domains following the same pattern but still said wrong symbols. But the rules in the config file doesn't look like the one you posted here

Also maybe currently it has a certain limit of domains it can add to the rule.
Anyway, I may check it again if they add a more easier way to add domains. I've been using SimpleDNSCrypt for few months without any problem and imported a huge blacklist containing 676044 domains and subdomains at the moment. Well, surely almost nobody needs such a huge list but what can I say, that's me and right now it seems there's no simpler way to do this in YogaDNS.