I'm not positive about doing it with a dashboard - a custom analysis widget doesn't give you that level of customization.
But you can make a connection event search and use that. The search constraints will be in the URL. You can also save it if you use it frequently.
You will then have a persistent URL with all the parameters necessary to identify connection of the type you want. It should look something like this:
https://<your FMC address>/events/?table=rna_flow_stats&constraints=service%3Dftp&workflow=Connection%20Events&page=0
