Siemens SINUMERIK MC Commissioning Manual page 81

Copying/pasting F-blocks
You can copy F-FBs, F-FCs, and F-DBs in exactly the same was as blocks of the standard user
program.
Exception:
You must not copy blocks from the folder "Program blocks > System blocks".
Nesting depth for F‑FBs and F‑FCs
We recommend that you do not exceed a nesting depth of 8 levels.
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB
Safety program of the F-PLC
3.9 Creating F-blocks
81