Hi,
In short, there is no way to do that in an automated way.
The reason is, that to implement such logic, the plugin would have to split the input phrase each time there are no results. In this case, the plugin tries to search for 3step42. When there are no results, it would have to start splitting and adding spaces, and doing more and more queries for:
3 step42, 3s tep42, 3st ep42, 3ste p42, 3step 42, etc..
In this case, maybe the 6th query would be the one you are expecting, but that does not mean that the 2nd, 3rd, 4th does not yield any results either. This single search would then do 6 times more queries to the server, possibly causing very long timeouts. For longer words it would take even more.
The only reasonable way is to add keywords manually to the post meta box.