Hello! This is a bit late, but maybe it still helps: Could it be possible that you are only changing relationship type (which has no influence on line thickness) but not the type of partners (primary, extra, ex)?
Primary partners are signified with a thick line, extra partners with a thick line as well, but they are always on the other side of their partner than the primary partner, and ex partners are having a thin line. This doesn't change, even when a person who is filed as an ex partner is given the "Married" relationship type, or when a person filed as a primary partner is given the type "Divorced".
You can change this by clicking on a person in said relationship, choosing "More Actions" (below the options to add siblings, partners, parents etc.) and then clicking on "Change partners". This allows you to change a primary partner to ex and extra, and extra partner to primary and ex, and an ex partner to primary and extra. Be aware that each person can only have one primary partner, and if you change the primary partner, the former primary partner will be automatically classified as an ex.
Editing how current and former partners are displayed is possible under "Options". However, this only changes visuals and not the relationship tag.
Hope this helps!
