Allow multiple objects to be selected on UI Graph

[TreeOfLearning]

Feature request: Allow for selection of multiple objects on the UI graph, to allow links and other connections to be seen for more than just one object at a time. This will allow the user to decide what level of clutter is acceptable, whilst allowing enough flexibility to see relationships between multiple types.

See discord discussion: https://discord.com/channels/841451783728529451/1078638002496082022