The children of tree are not displayed [PLEASE HELP]

I created tree model with one textfield and added test item. After that i added test1 as a child of test item but it doesn`t display anywhere, but i can find it by search.

Api response looks like this

"Example text":"test",

So, it shows that item has two children, but “children” field is empty.
Can you help me please with this issue.

This affects me also.

which api endpoint did you use?