The use case is like this. You accumulate some emails from person X. At some point you realize: “I want all these to get routed to a folder”. So you create the folder and the rule. What would be really handy is to be able to manually run that new rule on the existing Inbox contents, so existing emails would also be moved to the folder defined by the new rule.
Hi wwzeitler, I’ve not yet created rules in eM Client (only server-based ones) and so I can’t test it, but are you essentially after the “Apply” option in the Rules window? https://www.emclient.com/webdocumentation/en/10.0/eMClient/Default.htm#Rules/Apply%20rule.htm
Ah, there it is!
Just for grins I select “Select All”, then I click 'Run". Result: “no folders were selected”.
Ahhh, glad that sorted it! Afraid I can’t help you about the shy folders, though. 
If this has resolved the issue for you, you can click on the Solution option on the post and then that lets the eM Client team know they no longer need to look into this one. 