I haven't taken time to read all the posts, but when I saw the topic, I just had to reply and recommend Evernote - LOVE that app! Download to your computer and then add to your smart phone - storage is online, so it synchronizes your notes between your devices. And it's free!
Most of my stamps are from Papertrey Ink, so when I need to add a stamp set, I just copy and paste from the website. One of the best features is that you can search for a sentiment; say you need a birthday sentiment; just type "birthday" in the search box, and Evernote will bring up every set you have that contains that word.
I have a note set up for my Copics also, so no more duplicating markers, because I can look on my phone and see immediately which ones I already have.
This is the best organizational tool; you have a certain amount of storage per month; if you need more, you can get the paid version, which is just $5/month or $45/year. Plus there are other features with the paid version; I'm fine with the free one, so don't know what all those other features are.