The data for option lists can be loaded as part of initial data loading.
When gantt.load called, component request a data from server side, and such data can contain tasks, links and options for collections.
If you are using connector - you can use set_options method
If you are using custom code on server side, you can form necessary json or xml with your code.
There is no way to load data in lightbox dynamically for each task separately ( there is no built in way, with a bith of custom coding it can be implemented as well )
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