Seems possible yes but I only see this working for a task that is somehow memorized in a Homey variable or something.
The task creation would have to store the ID somewhere and the other Flow has to mark this ID as completed.
So maybe a card
Create a task ... with reference id: <my_reference_id>. And another card with
Complete a task with reference id: <my_reference_id>. Only problem would be if the Flow with the first card is executed multiple times you could overwrite a not completed task. Your reference id in this case could be something like
Some problems I see is statuses flipping quickly for some reason resulting in spamming complete and create.
I could give it a try next week to make something user friendly if I have some time.