Transformed columns do not show in the right group in dropdowns or at all (with data-groups=true)

[janagombitova]

After I transformed a few new columns when testing demo.akvolumen.org I noticed my transformed columns:

• In other transformation editor (like combine column) showed in the dropdown under the group Transformation
• Did not show at all in the visualisation editor dropdown

In this dataset: https://demo.akvolumen.org/dataset/6005a12f-3d29-4e35-8bc8-a7dbba103d47 In group: People Transformed example column: Age categories

Steps to take to reproduce:

1. Derive a new column, it does not matter which transformation you use to derive it.
2. The new column is added to the end of its parent data group, as expected.
3. Go to another transformation where you see the column dropdown - your new column will show under a group Transfromations and not in its parent data group.
4. When in visualisations the transformed columns do not show at all.