No need to reflash it, just boot with the MOSLO kernel&rootfs to repartition your mmcblk0. (remember you need to have enough free space on partition 1 for this tu succeed... and of course take backup of everything...)

When the partitioning is done and you boot the device, your ubiboot environment works just like before.

When you have repartitioned the device, you can extract the Nemo rootFS to your mmcblk0p4 either via the MOSLO export or ubiboot maintanance console. (or you can do it in the device console, whatever...)