Tripped over these commands today:
/run SlashCmdList.UI_ERRORS_ON()
/run SlashCmdList.UI_ERRORS_OFF()
https://github.com/Gethe/wow-ui-source/blob/live/Interface/FrameXML/ChatFrame.lua#L2348
Wasn’t able to get them to work as simple slash commands but this seems more straight forward than the C_Timer workaround.