There is an option to have 4 panes displayed at once which is a great help. Still need to switch between two tabs on each retainer but better than 20 at a time for sure.

I also think the retainers need a search function. The one they've added to the crafting menus is great where it tells you if you have the items but then finding it can be challenging. I recently found that I had 2 sub-99 stacks of the same exact HQ item were on different pages.

But seriously, look into the larger display. It is great.