It is very easy to group LEDs programmatically with some relatively simple code. Once you define the essential task, which is to replicate something n times which should be a clue to use a 'for' loop. A simple logic would be:
for all leds in sequence
{
for the size of the led group
{
set group colour
}
}
That can be set up with simple indexing, so start with led 0 and write out the group size number of leds, at the appropriate times incrementing an index to the current led number.
If you are hoping to run existing effects or animations through this mechanism, your first stop would be the documentation for the display library you are using to see if the library already supports grouping.