How to stop Defraggler in progress?

I set Defraggler to defrag my HDD not knowing it would take days. It's been 4 hours and it's only 4% done. Is it safe to stop?

I see no option to cancel. How do I even stop? Kill it in task manager?

Just close it using the X in the top right of the window, pause it first if you like.

I don't take much notice of predicted time-to-go in any app; they can be wildly out. (Even Windows updates jump from 0% to 100% in seconds).

How big is the disc? TB discs can take a long time to do a full disc defrag.

In Defraggler after doing an analyse click 'view files' then the tickbox at the top of the list, then 'defrag checked'.

That defragments the files and is quicker than a disc defrag.