My way of keeping my mnemonic phrase is I created an excel file on my google sheets, you can find it on your gmail. Aside from that, I also created a copy of it on my computer notepad that was saved on my drive. I also saved on my notebook, all important information and passwords are in there. I always do that incase I lost one of my saved documents. I experienced losing it before, so I learned from it and I feel secured on that way.