Make node selection more intuitive

[flourish86]

Describe the bug

It's not obvious how to interact with the search bar. For example, you have to guess how to add multiple elements at once.

To Reproduce

1. Click on add node, enable editing
2. Select a category, e.g. "Hosts"
3. Try to add multiple nodes, without knowing how to.
   3.1 Try to select how to select multiple nodes
   3.2 Try to confirm the nodes to add

Expected behavior

Make it obvious how to select multiple object from the dropdown and apply them

Screenshots