On Mac Endpoints (and on regular basis) you see a red sign on the Appstore icon when updates are waiting to be installed.
One of the benefits of an RMM system is that you can see what Endpoints needs attention, or force updates from a remote command, to make sure that Endpoints running the latest software.
I do not think this is possible with iTarian. The only way I would know of to manage Appstore apps would be if your RMM platform used the MDM feature that deployed all the apps on the endpoing (Mac machine). There are other Mac-Only RMM type services out there that may be able to update appstore apps with detected updates. However, keep in mind that typically the end user’s Appstore is tied to thier own Apple ID that is not tied or connected to your RMM.