You may want some of them to have image previews, some of them only to have a text box.
You may want to bookmark just images, PDFs or other media rather than web pages.
You may want to bookmark video URLs with their image previews.

You may want to bookmark images with their source URLs. That could instead mean that every bookmark with an image preview should have the image cached. With regards to whether you should keep image histories or not, I could say that you should make that decision based on your requirements (on how important it is) and your personal philosophy (how easy it should be to let go).

All of these could mean that you'll want to have certain templates for bookmarks: generic URL, generic URL with preview, image, video, etc.

You may also have area specific bookmark templates, for example, a unixporn URL could be accompanied by the URLs to its resources like the theme pack, icon pack and dotfiles in addition to its preview. The types of resources could be made extensible.

You may want to search only among the bookmarks with previews.

I guess without much effort, Anytype or a customized program that emulates it could do the job. I dislike Anytype whenever it deviates from Notion, except for the graph view. But I guess a dashboard with search can be better than a graph. A graph only helps uniquely for you to know where each components are stored.

If I make one:

Define the types of database parts I want.
Define the types of database views.
Define the components.
Define the visual layout of components.

And,

Define my personal dashboard structure (aside from making an extensible one like Notion)

Left-click: follow link, Right-click: select node, Scroll: zoom