Keep Feel Popup open when switching elements

[pinussilvestrus]

Is your feature request related to a problem? Please describe.

Follow up of #265

We currently close the Feel Popup editor once another element is selected, as the properties panel follows the pattern of always edit the current element.

However, for this purpose, we can imagine keeping the popup open, as it makes sense to keep the context in the popup but check other element properties. Example: Inspect other components and copy variables or code.

Describe the solution you'd like

Keep the popup open during switching elements. This would mean we would need to reference the element in the popup and execute updates on it. Currently, the entries always use the selected element to do the updates.

Describe alternatives you've considered

Keep things as they are.

Additional context

Related to #265