BotTracker ist a plugin to exclude and separately track the visits of bots, spiders and webcrawlers, that hit your page. Because Matomo (Piwik) doesn't store the user agent, BotTracker will only be able to track new bots from the moment you add them to its list forward (retroactive tracking isn't possible).
This plugin is still in BETA-status, but I have tested it for a while. It should be stable.
Additional info: I wrote BotTracker for my own needs but people ask me to make it public - so I put it online. It's free to use and I will support it as long as I can spend the time. But I will not activate a donation button. If someone is paying money, I feel like I have to support him. I want to work on this plugin because I want to and not because I have to. I hope you can unterstand that.