When reading, writing and deleting registry keys, there is no way to do anything with a registry key whose name contains a slash.
For example
HKLM
+----SOFTWARE
+----somekeywith/aslash
+----child
DeleteRegKey HKLM SOFTWARE/somekeywith/aslash/child refers (rightly) to a 4-node key - there is no way to specify the 3-node key
Perhaps support escaping with backslashes? e.g.
DeleteRegKey HKLM SOFTWARE/somekeywith\/aslash/child
Why are you using / slashes? This is Windows, use \ (backslash). Escaping would not help, NSIS passes the path directly to Windows.
Same case for \ in keys. In the case of App compatibility settings, windows itself writes \ in key names. https://blogs.technet.microsoft.com/mspfe/2013/11/21/disabling-dpi-scaling-on-windows-8-1-the-enterprise-way/ to use paths as keys
So NSIS can not clear those keys. Using keys with slashes instead is not recognized by windows here
That link shows slashes in the value name, not the ** key name** (registry path). Slashes have always been legal in the value name.