For some reason component tooltips (setTitle() method) is not supported in Button.
Shouldn’t it?
Hi, yes there is no such feature yet, there is feature request in GitHub here, go and give thumps up. There are also links to discussions around the topic
https://github.com/vaadin/flow/issues/4169
E.g. here is example of using Paper Tooltip with Button https://vaadin.com/forum/thread/17167582/tooltips-webcomponents-for-button