I've figured out two of my mistakes, which are based upon the fact that for AssignName.js and AssignPresetName.js, their respective ....Dialog.htm do not use the same name as the .js script. Using customui also influenced the problem.

1. When writing scripts, I developed the bad habit of renaming two scripts at once, for example: somexscript.js and some_script.htm, renamed to say _somexscript.js and _somexscript.htm, or somexscriptSAVE.js and somexscriptSAVE.htm, which works fine when both the .js and .htm have the same name.
In the case of AssignName and AssignPresetName, the respective ....Dialog.htm file has a different name, so there is a 50% or so chance of naming the AssignNameDialog.htm file to say _AssignNamesDialog.js which is wrong, and causes problems when present.

2. The second error is that when using AssignName.js, the AssignNameDialog CANNOT be named _AssignNameDialog.
( the PresetNames.txt file also cannot have an underline prefix.)

- Brian

My 3rd error was not copying PresetNames.txt to the MoI4Beta.

I think that I have been using the preview area of Windows (file) Explorer incorrectly as well...