Nested groups semi-working add during runtime

[marcortw]

I briefly mentioned this bug here,
but I thought it's ok to open a separate issue because I couldn't find an exact match with any other issue. The bug affects the current develop build
(c325418). It's not yet in master

• PR Nested groups order logic  #3206 seems to implement the possibility to add nested groups at runtime (fixes Timeline nested groups work incorrect if set them after timeline init #3126), however...
• when adding a newly created group "A" below a parent, the nested group "A" is not visually indented
• when adding a second new group "B" below the same parent (probably also applies if below a different parent), "A" gets indented, but "B" will remain on the first level.

Find an example in this plunkr based on the current develop build. After loading the initial data, click on the first button and then on the second button to see what I mean.

[yotamberk]

Thanks for reporting =)