Hi Petros,
Greetings from Syncfusion.
As you are loading more inline items in the row It takes time to generate tasks and render in the UI. Already we have a feature request on “Virtualization support in GanttControl”. It can be tracked through our Feature Management System.
Please cast your vote to make it count. We will prioritize the features every release based on the demands. So, this feature will be available any of our upcoming release.
If you have any more specification/suggestions to the feature request, you can add it as a comment in the portal.
Regards,
Rachel.