The custom frequencies are for live systems. When you're running a live system, you will get bars displayed at the system frequency.
What do you mean by loading historical custom frequency from a database? Are you not able to connect to your database or you're not clear how to feed them to RightEdge?
If I create a custom frequency plugin for 1-second bars can I display them on the chart, add them to a watchlist?
I still don't get how to load historical custom frequency bars from a database (or minutes for that matter). When I select a watchlist symbol and update the data, it immediately reverts to my data provider (which supports historical data).
I’ve also written a custom DataFeed plugin to work with my data provider (Nanex) and my TikFactory class. The IBarDataProvider datafeed interface supports loading historical data, but of course it only supports the int-based frequency enum, so it doesn't seem I can load bars below 1-minute. It looks like I could fool ITickProvider by feeding historical ticks/bars to RE through the feed.