Fix labels to keep them visible for long texts

Problem description: When we want to annotate long texts, the labels are scrolled out and are not visible anymore.

Solution: Labels should be fixed to the bottom of the page, to the right of the page etc (depending on the settings); there should be a checkbox be a setting to activate the fixing of labels.

Remark: This issue is the same as issue #2573 but is still open since 2022. Someone have replied with a code to add in the settings ("sticky" labels), but that functionality should be native.