I’m not sure if this helps but I thought of a different approach which puts the new entry input inside of a collapsible group that is within only the last cell of the repeating group (the visibility statement is 'When current cell’s index is repeating group’s: count").
This almost fixed the tabbing from the repeating group to the outside group (since now everything is in the rg) but for some reason the new entry input is first to be focused in the last cell, instead of the input entry submission above it which shares the cell. I’m not sure why this is, but if you can solve this and refocusing the new entry input - then that would do it!
I also noticed that if I don’t assign a workflow to the X icon, then the inputs are focused from input to input on tab (downwards), instead of input to icon to input to icon. As a workaround, you can place an identical X icon (hidden on page load), with the delete workflow, over the button that is visible on page load, and have the workflow icon only be visible when the User hovers over the icon without the workflow.
I also needed to create a workaround for when the User’s list of entries count is 0 (since having no entries in the repeating group would not display the create new entry inputs). To do this, I created a conditional statement which changes the data source of the rg to do a search for one ‘admin’ input entry. This allows the User to create an entry within the repeating group when their List field is empty.
I’m not sure if this gets us any closer, since I can’t figure out the refocusing, but just wanted to share incase it may help a little bit.