Allow more than 500 Tasks in a Project
Project is not allowing a project to include more than 500 project tasks. There does not seem to be published documentation of a limit to the number of tasks.
I support this idea. We are thinking about using one Project for the entire organisation, so that everyone is aligned and not working in siloes. However, having a limit of 500 tasks make this idea a non-starter. I guess there are performance trade-offs, but please consider. The same applies to the maximum amount of resources of 150. I guess we'll have to aggregate our projects to get to a single view (in Power BI), but that will require discipline in terms of naming convention and may not be practical.
You are correct that the limit is 500. You can find all the limits for Project for the web at the bottom of this article - https://docs.microsoft.com/en-us/office365/servicedescriptions/project-online-service-description/project-online-service-description