As Peter suggested, and based on your screenshot, the assumption is that the files are stored on a OneDrive folder?
I also use OneDrive as my 'go-between' from my PC where I edit backing tracks and lyric sheets, and my iPad where I run ST. I've got to the point where EVERY time I want to import something into ST from OneDrive, the first thing I do is go into OneDrive app and drag the screen down to force a refresh. Even then, I can often be waiting 15sec-2 minutes depending on whether I'm waiting for a 5KB lyric file or 40MB audio file to show up, or an updated version to appear in ST's import UI.
I'm more familiar with using Android tablets and have NEVER experienced such consistenly slow cloud sync and UI refresh performance like this.
In saying that, I think might install iCloud for Windows on my PC to compare the experience as it really drives me nuts.