Hello!
You can add some conditions to the Market Locator search template to narrow down the list of markets to be loaded.
However, they cannot be too complex because to check various market information, you need to request that information from the server, which means you are actually trying to refresh thousands of markets while searching for the ones you need. BetFair will certainly not be happy about this, and that's the main reason we've limited the number of markets you can have in the program.
You will have to find a workaround, e.g. look for all Match Odds, Correct Score and Over/Under markets but within the next hour only, and then use the scheduled market search to look for new markets every hour.