How can we improve WHMCS?

Search/Filter by configurable option isn't currently possible. You can search for a certain value in the top right search but there's no actual filter under Clients, such as in Service Addons. You can filter product addons to see which client is using a specific one, but cannot for configurable options.

You can add Configurable Option Groups and Configurable Options in Products/Services, but you cannot search/filter which client is using what.

Say you have clients using a dedicated IP address as a configurable option. You cannot filter anywhere to see which ones are using a dedicated IP address. You'd have to run a database command, or note it down somewhere. You can search for the IP in the top right, but that's one by one. We need a normal Search/Filter to be able to view all clients using any configurable option and filter through them.

This is another of the many missing features in WHMCS, which should have been included a long time ago without having to vote for an essential feature. There are forum posts with users asking how to search configurable options. It's a requested feature.