That is exactly how you do it, in Notepad
At the end of Op1 there are most likely some lines of code that look something like this:
M5 (Spindle Stop)
M9 (Coolant Off)
M30 (End of Program)
%
So normally all you have to do is put Op2 ahead of these lines. There are also normally a few lines of preamble code that could be removed from Op2
If you have a tool changer then you will need to insert the needed code for that. If you need to manually change tools, then keep it as two separate operations/programs.
The other option is to just create the separate operations in your CAM program and post them as one program.