Trash item in the bookmark panel will increase.
Items included in Trash in the bookmark panel are increasingly increasing.
I have not consciously deleted bookmarks. Items over 1,000 are included when I check the Trash folder after a certain time has elapsed. Probably it isn't a bookmark, it's close to history information.
In Windows version, such a problem has not occurred.
Vivaldi 1.7.735.46 on macOS 10.12.3.
I solved this problem self. Extension was causing problems. I solved it by resetting it.