Hello
All in all your sketch needs a time- and button handler for the led sequencer and debouncing.
C++ provides a lot smart instruction eg "struct" to built logical groups for the usage of User Defined Datatypes (UDT). The LED sequencer could be one of these contatining the timing and the ON/OFF sequence to be executed by a how ever contolled timer function.
Have nice day and enjoy coding in C++.