It appears that the file for where to save notes is simply alphabetical. This makes it challenging to be sure notes are in the right file when you are adding note after note and it's just another step to check.
I'd find it highly useful to have the following feature.
Option: Default Note File
Options: <Last Used> (just always populates the note file which whatever was last selected) and a list of note files to set a specific note file as the default.
Behaviors: Last Used simply keeps the last used note file. Take a note in "Notes 1", then next note you change to "Notes 2" and then on the third note the file is set to "Note 2"
Specific: Set to "Note 1", take a note and add to "Note 2". Next note defaults to be saved in "Note 1" file.
There may be a reason for the current behavior but I don't see any benefit (other than programming time, which is also important on the business side) to the end user over having an option to set a default note file.