I. Tools > AutoCorrect > AutoCorrect Options - Options tab.
[M] Replace while modifying existing text
[T]: AutoCorrect while typing
M and T should explain what it means if an option in the M or T column is selected.
1. Still not sure what M label is trying to express.
2. T label is closer, but does not indicate that "While Typing" has to be activated.
3. Possibly in combination with tooltips.
(Sorry, no good ideas to propose.)
( cui/uiconfig/ui/applyautofmtpage.ui )
II. Tools > AutoCorrect > AutoCorrect Options - Localized Options tab.
[M] and [T] appear, but no explanation appears.
(also looks like spacing under "Single Quotes" and "Double Quotes" is not following UI Guidelines)
( cui/uiconfig/ui/applylocalizedpage.ui )