This setting in Current Drawing Preferences is only for coordinate display and grid.
The input of fractional units in the command line or tool options is not supported.
There was a contribution for this feature, but because of side effects we had to revert this again.
Until you work in Inch dimensions, you can enter this:
2+7/8 , 1+3/16
This will work, because math expressions are allowed.
But when it becomes larger, you have to know the factors yourself.
E.g. for 5yd 2'3"3/8 you must enter something like this:
5*3*12 + 2*12 + 3 + 3/8
Math expressions should even work in tool options like circle radius or parallel distance.
We reverted the implementation because it was unacceptable when the side effect was detected (no
The plan was to refactor this with a more stable solution, but I can't say, if anybody is working on this actively.