We have customised tooltips that work on mouse hover, however it does not work with keyboard navigation. I have attached a video showing this within the example taskboard - https://bryntum.com/examples/taskboard/tooltips/
Support Forum
It's not supported now. I've opened a feature request to add that. Here is a link to track the status https://github.com/bryntum/support/issues/4722
All the best,
Alex