The SIMO pins VBUCK1, VRF, VDD_NS, VIN1 and VIND2 can be left floating. VCCD is Internal core regulators' (LDO) output. It requires bypass capacitor connection for proper operation. 1uF is connected on VCCD when VBUCK1 does not power VCCD. It is used as core supply input when internal regulators are OFF. Please refer PSoC 6 hardware design guide. The information regarding unused buck pins will be added in the document soon.