I have created a Power BI custom connector. This one works almost perfectly. However, with large dataset it is an issue when previewing and refreshing data in Navigator. It takes a long to view the different tables I am fetching through my API call. Is there any way to prevent all tables from loading at once?
First of all, I have to admit that I don't have experience in custom connectors, only some experience in Power Query. From your screenshot, the number of tables is not large, but the number of rows in preview is large. Is it possible to reduce the rows queried for preview in Navigator? Maybe you can only query top N rows for preview instead of the whole table.
Another option is to create Dynamic Navigation Tables in Navigator. I found below links that may be helpful: