Hey, my father was having this exact issue with Chrome 95. He has 100's of bookmarks in dozens and dozens of folders. It would load in the bookmark bar, bookmark Manager wouldn't load. I had guided him on backing up his bookmarks as they very precious to him. The Solution. Uninstall Chrome. Download an old version from File Hippo.
When uninstalling your current version of chrome. First take a copy of Bookmarks file from C:\Users\User\AppData\Local\Google\Chrome\User Data\Default
Copy it to a backup location.
When uninstalling Chrome, also ensure (Remove my data is not checked).
Then uninstall, install this version. Your bookmarks will load and bookmark Manager will begin to function again.
Export your bookmarks to an HTML file as you would have previously.
Then look to move to another browser, I'd recommend FireFox.
I will be subscribing my father to BookMark Ninja
This will mean his bookmarks are stored in the cloud, he will be able to access them from his iPad and Laptop. It supports larger bookmark collections and he won't have to back them up anymore. (Although I will show him how to anyway).
Happy browsing to you that like lots of bookmarks. (Not my jam)