Solved
Bug Report: STM32 H723ZG wrong register name, FTHVL <-> FTHLV
In some places the register name "FTHLV" is typed wrong:
The right register name is "FTHLV":
In STM32 CubeIDE the name is wrongly spelled "FTHVL":
In the Reference Manual RM0468 (Page 2227) it is one time called "FTHLVL":
And in another Diagram (Page 2213) "FTHVL":