Open menu "Tools/Options/Tag Panel/Tag Panel/Add field:
Field: GENRE
Name: Genre (edit field)
Multiline: no
Note:
This additional GENRE edit dialog displays a list of genre values from all selected files.
If you select one value from the list, and you save this status, e. g. by [Ctrl+S], ...
then the selected genre value will be saved into the selected files.
Note:
To see the existing GENRE values as a list, the additional GENRE edit dialog should be opened unfolded (mouse click on the dialogs arrow down button), ...
alternatively ...
within the additional GENRE edit dialog not unfolded, use cursor up/down to scroll along the items within the list of existing genre values.
Example panel dialog ...
DD.20180128.1850.CET, DD.20180128.1913.CET,DD.20180130.1150.CET