In the following "to select" means "click it with mouse" -- I didn't evaluate the behaviour of the dialog via shortcuts!
When I try to assign a shortcut to a macro via
-> Tools -> Customize -> Keyboard
-> selecting an unassigned key under "Shortcut Keys"
-> then selecting a "Category"
the first element in "Function" is highlighted automatically, but the "Modify" button remains inactive.
Only if I select another "Function" the "Modify" button becomes active. Now I could select the first "Function" again to finally assign the key to it via "Modify".
But this doesn't work if there's only one "Function" in a "Category" (for example in category "LibreOffice Macros" -> "LibreOffice Macros" -> "pythonSamples" -> "TableSample").
Then I must select another key "Shortcut Key" instead for the "Modify" button to become active.
Whenever I select another "Category" the "Modify" button becomes inactive again even though a "Function" (the first in the list) is selected automatically.
The behaviour is independent of OpenGL usage.
OpenCL cannot be activated on my installation (I can select but after the restart of LibreOffice it's inactive again).
IMHO the "Modify" button should be active whenever an assignable "Function"-"Shortcut Key" pair is selected.
Maybe there should not be an automatically selection of a "Function" on selecting a "Category", too.
Version: 18.104.22.168.alpha0+ (x64) / LibreOffice Community
Build ID: ac80ec817eb07c77a51bc0729985a473c734182e
CPU threads: 12; OS: Windows 10.0 Build 19042; UI render: Skia/Vulkan; VCL: win
Locale: ru-RU (ru_RU); UI: en-GB