Version: 2.9.9.4 Beta (899097) 64-bit - 18 Apr 2020
When you select an item in the binder, the binder will expand to show the sub-levels of the folder but the arrow to collapse the item will disappear while it’s selected/highlighted.
I’m not seeing this, but perhaps it depends on the theme you’re using. (I’m on Solarized Light.) Could you post a screenshot please?
Not experiencing this with the default theme, either.
I included a snapshot. I tried taking a video but I didn’t realize the forum didn’t allow for vids. Hopefully, the screenshot should illustrate what I’m talking about.
Dark mode theme. I remember this being talked about a few months back. Doesn’t look like to was resolved and I can’t locate the thread where it was mentioned. 
I’ve tried a number of themes and find the same problem in all of them except Default. I believe this has been the case ever since Themes were introduced.
It seems I misunderstood the issue.
Yes, I’m seeing the same thing with Solarized Light. When a binder item is selected, the arrow disappears.
Best,
Jim
This has been filed. Thanks.