Variable Groups disappear from Editor System panel list?

I'm trying to work with "Variable Groups".
Now I have 2 owned Groups added in my World, so that I can see them from "System/Variable Groups" both under filter "Added to World" and "Owned by me".

Test-1, I tried to add or remove some Variable in one Group.
That's say, if I have 3 Variables, outer Groups list shows "3" vars under the group name, and "3/150" shown at the header of inner Variable list.
When I add 1 var, they become "4" & "4/150", so far so good.
But when I delete 1 var, they become "4" & "3/150", the outer info is wrong. (Okay, it maybe just a text.)

Test-2, I tried adding over 150 variables, I add 10, delete 3, add 143, now it's 150.
The 151-th var can't be added as expected, and texts show "153" & "150/150" as Test-1.

After my testings, I'd like to dump the unused testing Group.
I click "Remove from World" from the "Added to World" list, without "Delete" from "Owned by me" yet.
BUT, THE OOPS HAPPEN!!
The "System/Variable Groups" shows NOTHING but empty msg!?
I tried "re-enter World", "re-open Editor", "re-start Windows, "re-login Account", "re-install Editor", but nothing help.
it becomes UNABLE to see, add, edit any of Variable Groups now.

Btw, in my real case, I have another existed Group which shared and added to a collaborating World owned by other colleague.
I cannot see any Variable Group in any World from my Editor(s), includes 2 PC logged-in with my account.
But, my colleague, who can still see & edit my shared or their other Groups.

Thanks a lot for any help.