Here's what I do.

Download the Blank Sidebox mod.

Unzip it twice to my local computer, in different directories.

Leave one as the mod writer created it, except changing the folder under templates to my custom template name. That gets uploaded as blank sidebox.

On the other, I change every instance of 'blank' in all the files and file names to another name (blank2, say) and that gets uploaded (and recognized in admin) as the blank2 sidebox.

You can have as many as you want doing this.