The 'Repeat Step Sequencer' option does not exist in FL Studio 12. It was removed as the Step Sequencer and Piano roll were merged and are now different representations of the same underlying Piano roll data. Prior to FL Studio 12 they were separate data-systems and this allowed Step-channels to operate independently of Piano roll channels. One advantage of the merge is that now you can swap from Stepsequencer to Piano roll view and back again. This was previously impossible. The downside is that you can no longer repeat one Channel as a shorter loop than the others in the Pattern. They must all loop together.
1. Keep your step sequenced parts and your melodic parts in separate Patterns in the Playlist. Then you can repeat a 1 bar step sequence along side a 4 bar melodic part for example.
2. There is a new Time marker available for Piano rolls, type 'Visual length' will change the active Pattern length. This will however will only allow you to shorten long Piano roll Channels to match a shorter Stepsequencer channel.
We are looking at adding this functionality back in a future update to FL Studio, but it requires some considerable development to implement it under the current structure.
Image-Line Support Team