Let Notepad Plus Plus start always by opening a default document you can decide
You may work with Notepad Plus Plus using most of the time a particular document, even if it is about a file you need for temporary editing work, something like a scratch pad.
Having a default document lets you start working immediately without the need to care about giving your file a name and selecting a folder to save it. As you may know Notepad Plus Plus in its Preferences offers to remember you last session, any files that were open just before you closed the program, to open them again automatically next time it runs.
If this session-memory does not cover your needs and you prefer to open a particular file by default, then right click the Notepad Plus Plus entry in your Start menu and select the “Open file location” option. Then right click the Notepad Plus Plus shortcut and go to Properties > Target. After the address of the Notepad executable just add the address of the file you need to make default. For instance: “C:\Program Files (x86)\Notepad++\notepad++.exe” “C:\anyfolders\MyNotepadDefaultDocument.htm”
Note that if after this change you select to pin also Notepad Plus Plus in the taskbar, this icon will let you open by default a particular file whenever your run the Notepad. As you guess, you can follow the same way to let other programs too run by opening a default document.