help!!! how can I separate stacked items?

I have 5 stacks of 20 keys in my storage vault box. I want to withdraw 5 keys for each of my characters. How can I take out just 5 keys instead of the entire stack? Right now I feel like the only way is to get a trusted friend to hold part of my inventory while I put the other part into storage. Then I put the first part into a different slot of the storage. How annoying!

I don't like having to rely on others to separate my stacked inventory. Anyone know how I can do this by myself without too much hassle?

Thanks in advance.

i think that your solution might be the only one : (

I just keep the useful stuff in storage and as i change characters i grab it up then return it when done