Soc/efuse_reg.h - no such file or directory

Hi the above message has wasted my afternoon. Naturally there were three copies of the file in the folder structure of Arduino/packages/ESP32, and after a while spent fixing a filesystem fault, (Apple Operating Systems are no longer reliable) all of them could be opened by a user. So I followed the instructions on a previous post and deleted all the offending packages and reinstalled them (with restarts at each change). Now I get the same warning, but now it is accurate, the folder structure (now moved to my Library) does not contain the file.
Does anybody know how to find the parent Library item to install, or how to find a header file that is demanded but not on one's computer?
There's no point in copying the error report- it is many times longer than the code for the sketch, and as there is no such file on the computer I can't dispute it.
Please help.

These kinds of problems are either due to wrong board specified, or wrong library, or a user messing with the system.
It is totally normal to have multiple copies, that is how the 3 level concatenating library system works. You pick one via the board selection. Try supplying some information like board used, all source code in code tags properly formatted with Tools/Auto Format, entire error log also enclosed in code tags.

@sonofcy, Thank you for replying. I was drying to load a sketch to identify the version of the board; it is an ESP-ROOM-32 but there are no matching boards in the boards list. The supplier's manual instructs the user to declare it as a "ESP32 Dev Module" which I did and successfully loaded the blink sketch to it. I successfully forced the IDE to see the "missing" .h files by copying them into the folder with the sketch. Having reluctantly found the files the sketch then failed on a "not declared" warning so I need to find all the library files it has called and edit them. Frankly as a two minute exercise in chip identification it has failed and I don't fancy spending more time troubleshooting it.
i would not advise anybody to delete the files in Arduino/packages/(boardtype) in the hopes that reloading the boards with Boards Manager will repopulate the folders. It does not, it populates a different folder structure (in Mac the user's Library, (in Windows perhaps the User's Application Data subfolder for Arduino's IDE). Luckily I have a backup so can copy it all straight back in.
As I am retired I have enough time to first reinstall the board packages starting at 1.0 and updating each installation by one version. Maybe this will populate the newly empty folder structure with the contents of a freak package.
Also, if you have a Mac, it is no good moving data out of a location to stop the IDE calling it, Apple's filesystem tracks these changes and simply opens the file from its new location.
Going to try the rebuild before re-loading the sketch.
Cheers
Fritigern