The Super Dracos are only intended to be ignited once, either for a launch abort or a propulsive landing.
I suppose they might retain the ability in case of a chute failure, but that would be it.
I'd still like to see them try it.
https://twitter.com/iamkostmos/status/1104510464627625984
I hadn't heard any thing from official channels since then.
read: NASA says it's not happening.
During a propulsive landing, the Dragon capsule would test the SuperDracos while still at a reasonably high altitude; this way, in the event of a failed SuperDraco, the parachute backup can be used. (The landing burn for Crew Dragon would start only a few seconds before landing, far too late to deploy the parachutes if the engines don't perform properly.)
That said, this is old information, and many things could have changed since then.
After landing there would be a process to make the craft safe by releasing all pressurised gasses, and either sealing or burning off remaining propellants. With no pressuring remaining there is no way to repeat this anomaly.
There will of course still be issues with the residual hypergolics since they are highly toxic and the propellant tanks will need to be decanted: whether than happens before or after crew recovery is another discussion.