Google Sheets: have the user draw in a box

So, it's a bit difficult to explain what I really need here.
I am trying to create an electronic record for the school I work with, but they require some specific things.
I added the date selector in the first row "date". That was easy.
Now, however, I have to add another function to the final column.
We work a lot with teachers in joint presence, so we need to get their signatures. I thought I could turn the last row into something that opens a dialog box that allows you to "draw" (here we talk mainly about the use of smartphones) so that you can "sign" each time we join, but you have not had luck with that still.
Can someone help me here?
Thanks and hugs in advance. 🙂enter the description of the image here