Apple Disk utility does not have this ability; only the ability to convert HFS+ to APFS.
The only other way is to destructively reformat the drive. BUT in Mojave, once upgraded to APFS, DIsk Utility no longer gives you the option to reformat back.
Apparently Paragon has FREE software that will convert APFS to HFS+ non-destructively, in other words you do not lose any data (do not trust any software , especially if it has the ability to destroy your data. Backups are always still recommended).
Check it out here: https://www.paragon-software.com/home/apfs-hfs-converter/
NOTE: I have not tried it personally.
Apparently Paragon has FREE software that will convert APFS to HFS+ non-destructively, in other words you do not lose any data (do not trust any software , especially if it has the ability to destroy your data. Backups are always still recommended).
Check it out here: https://www.paragon-software.com/home/apfs-hfs-converter/
NOTE: I have not tried it personally.
How do I convert APFS drive to HFS+ without reformatting?
