Your split or merged files will end up in one of two tabs, depending on your import method:
Click on a file to process it. You can split it up first by checking the box and clicking the button 'split'. Merge several pages from one file by checking them and clicking the button 'Merge'.
This is where files end up that were sent to the 'Split' email address, files with more than two pages that were split in the 'To be processed' tab or imported files with more than 99 pages.
The Splitter has two features. Check 'Process as separate files' (Ctrl key) to put all selected pages as separate files in the 'To be processed' tab.
Check 'Fast grouping' (Shift key) to send the selected pages as one file to the 'To be processed' tab.
Please note: files larger than 99 pages are ALWAYS sent to the 'Splitter' tab, even if they were sent from the 'no split' email address.