After pressing the check button (DONE), enter the reference, date and time on the next line.
It will be displayed in the Journal’s Linked References, so you can know when it was DONE.
For repeat tasks, the number of times is displayed on the right. Click on it to see your history.
The idea is about to become a reality.
With Task completion plugin, you can put the date on the next line after DONE.
I am also making a plugin. Logseq repeat-task reference plugin