I found this article very helpful, thank you.
I have a question concerning the $(Server) variable used in the arguments section when creating a new tool shortcut. There is also a $(Database) variable that I got lucky in trying when adding a tool link to SQL Server Management Studio. I was curious if you knew of any other variables like these.
A great one would be for the currently unsaved (therefore temporary) file you're currently working on to open when selecting a text editor like Notepad++. This would have to be a file path. Just thinking 'out loud' here.
I answered my own question by clicking the ">" next to the textbox, this give a context menu of usable variables