Question?
How and where can I store these two sequences so when I press enter in the serial monitor takes and executes the first sequence only, if I press again enter will take and execute the second sequence....
It CAN, actually, be done more or less as you describe... but not easily!
First of all, instead of "press enter", I would wire a button to the Arduino to say "do next", over and over.
Start with a program which will always have just TWO sequences, repeated. You COULD set things up to send "how many steps in pattern before it is time to repeat" to the Arduino from the serial monitor... but it would be messy. Easy enough to do a few variations on a SIMPLE program, each variation dedicated to doing patterns with a particular repeat number.
... and then have it go back and execute the first sequence, and so on.
This is easy if your program only ever does two sequences, i.e. repeats after second. (Most of what you need in in one of my other posts). And it is easy to have several versions of the program.
Once that much is working, it wouldn't be TOO hard to go back, modify the program to read one more byte from the serial monitor, right at the start of the stream of commands, and have that determine how many sequences to do before going back again to first one.
By the way... number things, and count FROM ZERO. So: the first pattern is "pattern 0" and the last one, when there are two sequences repeated over and over is "pattern 1". Seems odd at first, but has advantages which will become clear. And isn't so very hard to Just Do in the meantime.
You'd store the sequences in variables in the Arduino.