Better Anchor Links Widget has no checkbox

I just can’t seem find out why the widget does not have a checkbox to set it to sticky.

As I can see this plugin is not following standard widget initialization procedure (it is not extending class WP_Widget). That’s why plugin’s checkbox is missing!

Try to fix this widget through custom html id list (on plugin settings page).
Enter in textbox this id:
better-anchor-links

ah, I tried using it’s class name, that’s why that field did nothing.

if I set this widget sticky through the html id list it works, but only as long as I don’t set the check boxes for the search widget and the custum menu with page quick links. If I through these into the mix as well, they overlap better-anchor-links when scrolled all the way up, then overtake it on scrolling down. Besides them following smoother and the order being rearranged, from that point downward it works.

I unchecked their checkboxes again for now as I guess this is better than leaving it broken, but I could switch them on to show you for debugging purposes.

Widgets defined in custom list displaying before standard widgets.

In your situation the best way is to use custom list for ALL widgets:
Uncheck “fixed widget” option for all widgets, input their ids in custom list, use id order as widgets order in your sidebar.