Any idea how I can Git clone to the Arduino library for IDE 2.x on W10?
I can do this on my Linux machine (just cd to ~/.arduino15/libraries first) and it is a great way of installing large external libraries (and keeping them up to date).
On Windows there is no ‘libraries’ directory under Arduino15 (which is the IDE2.x) but there is for IDE1.x (C:\Users\\Documents\Arduino\libraries).
So at the moment it looks like the IDE 1.x is more useful to me on Windows, which is a shame.
This should equally work for Arduino IDE 2?
Doesn’t seem to - I’ve Git cloned a library there and it appears in 1.x but not in 2.x (Library Manager).
For info I’m using W10 LTSC, and (as you’d expect) had 1.x installed first.
Can't confirm this at all.
For testing I've downloaded a library that was not installed into the abovementioned folder
https://github.com/adafruit/Adafruit_AHTX0/archive/refs/tags/2.0.5.zip
And it shows up in the examples just as I expected.
Ah, yes, it seems that the Libraries folder (for ‘Custom Libraries’) is created under the ‘Sketchbook location’ - as set in Preferences (as you show) and this is true for both versions.
I had changed the ‘Sketchbook location’ in 2.x though to one that made more sense, to me at least - I’m a bit old school and generally don’t use the (‘you will conform!’) Windows ‘Documents’ etc. folders. 
So, I think I have proved that it is possible for a user who updates to 2.x to then get thoroughly confused !
Many thanks for your help. I hope this topic helps anyone else with the same issue in the future.
Arduino IDE 2.x does indeed create that folder on the first run after a fresh installation. However, it won't mess with it after that, so maybe you deleted it at some point?
However, the question is moot because you should not use that location to install your own libraries. That folder is only intended to be used for the fundamental "built-in" libraries that are expected to always be installed.
You should always install libraries to the libraries subfolder of your Arduino sketchbook folder.
Thanks, I get that.
If you change your Sketchbook folder though in Preferences you would have to install your custom Libraries again?
On reflection it would be good to have the option (even greyed out but enabled with a check box) to allow the (competent) user to choose a static, unchanging custom library location.
I use IDE1 and IDE2 back and forth all the time. The Libraries are only 1 copy and used by both IDE's. I don;t knw what you did but it didn't help.
Nah, just copy the contents of the previous folder to the new location.
If you don't want the location to change, just don't change the "Sketchbook location" preference.
Each version series does use different locations for the "built-in" libraries. In Arduino IDE 1.x, they are bundled with the application installation, under its libraries subfolder. In Arduino IDE 2.x, they are instead under the data folder (e.g., /Users/<username>/Library/Arduino15/libraries).
