slashed digits in figured bass doesn't work

Dear community,
I want to enter slashed digits in figured bass.
I've read in the manual:
Slashed digits or digits with a cross can be entered by adding \, / or + after the digit (combining suffixes); the proper combined shape will be substituted when leaving the editor
But I don't get the desired result.
I use musescore 3 on a linux (ubuntu) machine.
Thanks for Your help,
Stefan