1.
Open Find in Files dialog in an EmEditor window. Then, with the dialog open, close this window. All the windows of this process will be terminated!

2.
Single-process mode.
Open the first window by any way without using the command line option /sp.
This process (A) reads the Recent File List from the registry only when its first window opens, and saves the list to the registry only when its last window closes.
Now run a new process by using /sp.
This process (B) always synchronizes the Recent File List from/to the registry.
So, if A is closed after B, All the changes of the Recent File List in the registry changed by B will be overwritten!

3.
Opening the Recent File List menu in a new, independent-process window will cause all the pinned files to be removed from the menu!

4.
In a Find-in-Files result, a path will not be highlighted (or highlighted completely) if the file name contains such a regular expression match:
\(.*\)\x20