@Ashutosh Kumar Try to draw the schematic of the sub block, add the desired pins (iopin.sym, ipin.sym, opin.sym) then create the symbol automatically with

Symbol-> Make Symbol from Schematic

. This ensures the symbol is formally correct. You can then edit the symbol to change the shape/move pins as you wish.

thank you @Stefan Schippers i will try this way and get back to you soon