The Help windows displaying keyboard shortcuts still have many errors. While a large number were fixed in LR 12.1, many were not, and some new errors were introduced.
The Any Shortcut plugin's Analyze > Analyze All TranslatedStrings Files generates the file "errors.txt" (attached) containing all these errors. It should be run before every new LR release. The plugin's option Correct Help Keys In TranslatedStrings Files will automatically fix all of the errors.
I've summarized the errors below, with explanations for what's gone wrong and how to fix them.
The help keys for shortcuts containing Delete (Mac) / Backspace (Win) need to be specially encoded -- they should refer to Delete or the localized version of Delete (if there is one). LR will automatically translate that to Backspace (or the localized version of Backspace) on Win.
Many instances of help keys incorrectly contain Backspace instead of Delete. This causes Backspace to appear in the Mac Help rather than Delete:
The following corrections need to be made to these occurrences: