https://dataedo.com/kb/tools/heidisql/find-table

I'm read the article, but how to flush autocompletes from filter list?

How to clear items?

I think this is a misunderstanding. That "Clear" menu item in the dropdown menu does exactly the same as the right button on the edit box:

"Clear" item removing from input, but how to clear the list (filter history)?

There is no way to clear the dropdown menu (apart from using regedit, but that is on your own risk).

But I admit that usability probably says that "Clear" menu item should clear the drop-down, not the edit box.