Hi Arnaud,
I created two links in my flowcharting diagram, one via draw.io on the logo icon, and one via a rule on the business building icon. Both are shown in white over the diagram, both when editing rules (first figure, below its icons) and also when in view mode (second figure, once on the right of logo icon, three times on the right&above building icon).

This started after using the inspector, I only seem to be able to get rid of it by re-loading the grafana web-page.

Kind regards,
Dennis