This is a universal tip, doesn’t matter what kind of work you do, what country or if the issue is minor or major.
On the day the incident happens, send yourself an email. Title it “File Note – [Date]”
Then write as plainly as you can what happened. For example, “my manager made an unwanted sexual advance towards me”.
Then you can write how it made you feel. “It can me feel uncomfortable and afraid for my personal safety”.
Obviously use a personal email address.
If you are in a situation involving HR, lawyers or the like and you bust out a bunch of file notes in this format, it will greatly help you.
Even if you don’t feel like you will ever need it, get in the habit. Even the most minor of things.