fileOpen := false
^+b::
if not fileOpen {
	fileOpen := true
	FileCopy, Backup\Notepad++\config (PostIt).xml, %A_AppData%\Notepad++\config.xml, 1
	FileCopy, Backup\Notepad++\NppExec (PostIt).ini, %A_AppData%\Notepad++\plugins\config\NppExec.ini, 1
	Run, "C:\Program Files\Notepad++\notepad++.exe" "C:\Path\To\PostIt\File.txt"
} else {
	fileOpen := false
	FileCopy, Backup\Notepad++\config.xml, %A_AppData%\Notepad++\config.xml, 1
	FileDelete, %A_AppData%\Notepad++\plugins\config\NppExec.ini
}
return

The config (PostIt).xml is the file with my PostIt NP++ configuration (i.e., no title bars, line numbers, etc.) and config.xml is my usual NP++ configuration. The NppExec (PostIt).ini file is the configuration file for the NppExec plugin, which launches a script on startup that contains the following:

NPP_CONSOLE 0
NPP_MENUCOMMAND "View\Post-It"

This now seems to work as I want it. Thank you both for the help.

You may be able to do something similar with the NppExec plugin; I wouldn’t know the details on that.

@Matej-Vitek

For NppExec, put the following in your startup script (Plugins => NppExec => Advanced Options… => “Execute this script when Notepad++ starts”):

NPP_MENUCOMMAND "View\Post-It"

Cheers.

I don’t think Notepad++ supports opening in Post-It mode directly, and as you’ve observed, that mode isn’t persistent between runs.

You might have luck using a scripting plugin (e.g. PythonScript) and having a startup script that executes the Post-It command, e.g. notepad.menuCommand(MENUCOMMAND.VIEW_POSTIT).

You may be able to do something similar with the NppExec plugin; I wouldn’t know the details on that.