@CennoxX
Thank you, that’s a very simple way of achieving what I need, will definitely try this. Only downside is that I want to keep thd Master file as is, to use for comparison with future new music lists. Could make a copy for your procedure, then add the new music to it, for the next new music comparison.
However today I used this procedure, works well, adapted it from the one posted.

With new music file
1-use Edit Sort lines lexicographically Ascending, just for clarity
2-Highlight all lines then use plugins ‘remove Duplicate lines’, as there are always some duplicates
3-open original Master file and new music file for comparison
4-Use compare plus and ‘Compare’
5-Then use Diff Visual Filters… to hide matches
6-Use find unique lines
7-copy all selected visible lines from New Music, paste into a new file, to keep them separate, then copy into the Master file, for comparison with the next New music file.

Hope that makes sense

This gives me a new file with all new music without any duplicates that exist in the Master file

@PeterJones

Thanks for your reply. I will give your solution a try as a Macro learning experience. Maybe I’ll find other uses for it.

But, I just came up with a different solution:

I like Notepad++ so far, so I used the preferences to set Notepad++ as the default for a small number of file types I use occasionally. I renamed the extension of the file I use as my daily journal/log from .txt to my initials .th. I used the file properties to open that file with Windows Notepad.

It’s working well for me. I can use my journal/log with Windows Notepad, and everything else uses Notepad++.

@dfs ,
We could go a step further and lament that it would be nice if the entire graphical environment of NP++ could be contained in one dialog setting, and then when we switched between Light or Dark, the environment would change all the UI references:

Settings->Preferences...->Dark Mode,
Settings->Style Configurator...->Style:, and the
Settings->Style Configurator...->Select theme:

…could be coordinated to make just switching between Dark Mode and Light Mode change them all, accordingly. As it is, I’m glad to have just found out that the Dark and Light language files can automatically change by setting that one switch in the dark mode file @PeterJones mentioned, and that automatically chooses the correct code coloring file for the environment (Dark/Light) chosen.