Actually in my case, I am dealing with AMBA busses. Therefore, I just need to use the IP integrator at the end of the day.
Actually I have used Libero SoC SmartDesign before. In there we can put in an inverter symbol quite easily along with flip flop and other things. They are all found under Primitives section of the IP catalogue. Also, we can tie IP block inputs to low or high, or mark them as unused, quite easily as well by just right click on pin and select the right option. However, I can see that it is not like that here in IP Integrator. This is quite a big surprise for me actually.