Which visualization for events in time without timespan?

I would like to visualize device events (emergency button/reset button presses) over time. I have a simple table (MariaDB) with a rows containing a timestamp and a button identifier.

I tried using the “State timeline” visualization but that really doesn’t work. I had to create a variable for all possible buttons and then iterate in panels over it. There is unnecessary space between the panels and since there is no actual ‘off’ event the states never end.

I am looking to get one panel with swimlanes for each button. Suggestions for a better approach are also welcome.