Congratulations on launching Zapmarks!
I’m a big fan of bookmaking services. Having better ways of managing your saved information is important to me. I run https://trackr.sh that serves a similar goal.
Why did you pick a single keyword to identify your bookmarks? I use a similar workflow in Firefox vit found that it doesn’t scale for a lot of bookmarks. For https://trackr.sh I chose to go with a multi tag combination where you select a number of tags to narrow down your list of bookmarks.