The subliminals you find here at Indigo Mind Labs are ordered according to the technology generation they are built from. Lower levels of technology are less powerful and require less focus and energy; at 5th Gen and above they attempt to use all available resources to achieve their goals.
Therefore, you can (but should not) use as many as 3 subliminals of 3rd Gen at a time together, or 2 of 4th Gen (or 3rd and 4th Gen) at a time. I say you should not because this divides focus and weakens the program for achieving the goal with the best possible speed and impact.
At 5th Gen and above (5G, 5.5G, 6G) you can only use one program at a time. Do not mix programs or use more than one at a time. If you are using a 5th Gen, 5.5 Gen or 6th Gen program, use it with nothing else.
I am currently attempting to find a way to make it possible to use multiple titles at once for 5.5/6G but so far it is not a wise or safe thing to do. Don’t do it, no matter how tempting it may seem, unless and until I specifically say it is allowed.
Also, you should never use subliminals from two or more different subliminals creators at the same time, regardless of technology generation, as the scripting techniques can conflict and create all sorts of unexpected and difficult to detect or explain problems.