My org is switching from Slack to Mattermost. We’ve been working on a Slack app that manages PTO requests and shows a calendar of upcoming PTO.
Best I can tell from poking around the docs, to do something similar, we would need to make a Plugin, not an App.
Seems like the only custom UI you can do with Apps is modals (or adding buttons), but that there’s nothing along the lines of Slack’s Block Kit API for creating a ‘home’ page for your App out of limited building blocks.
Is this correct, or am I missing something?