it is required to displayed transfer function of sub vi, on front panel for main VI.
Sounds like you want a SubPanel. It's a control primitive under containers that allows you to display a running VI inside another VI. There is an example VI "Multiple VIs in a Subpanel.vi"
If you are just trying to duplicate the content of the indicator, just duplicate it on the main VI create a reference to it and pass that reference to the sub-vi. Whenever you want to update, write to the VALUE property of that reference.
If I understand you correctly, you want to show the 'block diagram' part of the transfer function on the main vi front panel. If this is the case, the code reference at link https://decibel.ni.com/content/docs/DOC-13859 may help, but I would ask you to consider what is the purpose and behaviour of this display. If it is a static image (never going to be changed / will change rarely), you may just take a screen capture and save it to a JPG file. Then, read the image from file and display it. If it is going to be changed frequently, you may need to consider using the reference code or perhaps doing something else eg print block diagram to files, and loading back the files to a picture indicator. I have never tried before, but I think it may work.
