The app is not really suited for such a task, and it is unlikely that eBay will be able to set it up to do exactly what you want.
You may be better off using a browser, preferably a desktop browser, that allows you to open multiple browser tabs so that you can switch between them quickly and easily to adjust your bid amounts or decide whether or not to submit a bid.
If you open multiple tabs and enter bid amounts in advance, and you do not need to change your bid amounts, you should have enough time to switch between auctions if the auctions are not closer than about ten seconds apart. Any closer than that and you may not be able to refresh the page after the end of the auction and be sure you are seeing all the bids that eBay has received before moving on to the next listing.
I have used that technique to bid on several items that were ending within about a minute where I had a target price in mind for each item that I was willing to pay, but I also had to ensure that I did not spend above a certain amount in total, regardless of how good each individual deal was, so that I did not continue to bid once I reached my total amount.
Or you can decide how much you are willing to bid on each item in advance and either submit your bid yourself or set up a sniping service to bid on your behalf at a preset time. This is harder to do if your bid or the amount is contingent on the results of other auctions ending in quick succession, though.
There may be sniping services that allow you to group your items and coordinate your bids in various ways. The simplest would be to submit a list of equivalent items and an amount you are willing to spend, and allowing the sniping service to submit a snipe bid as each item ends until you win one, and then stopping. But there may be other possible arrangements; I have not studied the available options, as I only bid manually.
