In a line chart where markers are set to be not visible.
There is no way to increase the hit box of a marker (or line) to be hit if I want to trigger the tooltip of the marker.

The mouse hover obviously works better from it's inherent logic (a click not beeing involved), but triggering the tool tip with a touch gesture seems quite fumbly. One has to hit the line very exactly. Up to a point where one has to try several times to make it happen, which makes it very impractical for new users who might not even know that there are tooltips to be displayed.

For further infos here is my forum thread with more details:

https://www.telerik.com/forums/how-can-i-modify-the-hitbox-for-tooltips-in-linecharts-for-a-touchscreen-device

As described there, increasing the marker size does only work when markers are visible.
Making the line thicker might help a little but comes with unwanted optical changes which are impractical for most usecases.

Best Regards,

Leo Härdle