Note: for Looker-hosted instances, this option will only work if the table takes less than 1 hour to rebuild (due to browser timeouts).
When you query data from a persistent derived table in Explore, there will be an option in the gear dropdown in the upper right to Rebuild Derived Tables. Clicking this will cause all the persistent derived table(s) referenced in the query to immediately rebuild, as well as all PDTs that those PDTs depend on to rebuild.
Another way to look at it is that clicking Rebuild Derived Tables ensures that this query will be run with all the freshest possible data.
Note: Clicking Rebuild Derived Tables will cause the PDTs referenced in the Look to be inaccessible for only the user who clicked the button while they rebuild. While they are building, all other users will be able to query the already-built tables. Once the tables finish rebuilding, all users will be querying these new tables