Hi Hans180,
Valid concern. I assure you that your trust is something we do not take for granted and are continually doing our best to earn it.
I understand that seeing something not work may raise your concern. However, this particular issue is implying bad user experience not security risk. It is caused because Microsoft recently released new version of Microsoft Edge which opposite to older versions is now built on Chromium and we did not implement the new logic for import yet. I will check with the team what is the status of this task and if we can prioritize it.
To answer your question. To ensure safe browser is really safe our team is monitoring all the threats that are out there and is fixing all discovered vulnerabilities and is proactively developing new security features with upmost priority. If you have any other concerns why you do not trust our browser please let us know, we would like to hear why.
Btw, I tested imports from Chrome and Firefox and both worked as expected. Let us know if you experience any troubles with those and also please share a diagnostic information (secure://settings/diagnosticInfo) and version of the other browser so we can investigate it.