The notes both have the same Voice Column Index. Select one of them (grab it by the stem!) and turn on the Voice Column Index property in the bottom panel. Then increase the number there by 1. That will move the selected note to the right of the other note.
If you so wish, you can then go back to the Note Spacing Tool and you’ll find that each of the two notes has a separate handle.
to set both notes to the same Voice Column Index here is a small script
place the *.lua file in your script folder
select the 2 notes you want to overlap in write mode
launch the script from the script menu
done
the script will switch to Engrave and go back to write after