Ability to add CanvasObjects to the right part of Tab containers

[matwachich]

Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

Not really a problem, but adding some controls to the right part of the Tab containers would be nice.

Is it possible to construct a solution with the existing API?

Impossible.
We must add a controls row on top of the Tab container, this is a waste of space.

Describe the solution you'd like to see.

[andydotxyz]

Impossible.

Technically this is not impossible as you could use a stack container and position the items very carefully, but it wouldn't be pretty and only works as long as the "waste of space" is available.

This could be a nice addition and it could mirror the Api for Entry accessories perhaps?