I use Firefox bookmarks extensively. Bookmarks handling has clearly not gotten the attention it deserves. Its deficiencies, some of which could be easily dealt with, frustrate me continually. Improving bookmarks would make Firefox a better and more useful tool for persons who use it to manage large amounts of information. Here are some changes I'd like to see.
1. Make the location of newly added folders (left panel in Library) user configurable to be top or bottom of the list. Firefox has long added new items at the bottom, which has always seemed wrong to me. Keeping new items at the top where I want them has taken a lot of ongoing effort over the years. Let the user decide what makes the most sense for how they work. Likewise, position to the top or bottom of the Library list in Manage Bookmarks (Ctrl+Shift+O) based on the user-specified preference for where new items are added. Firefox recently inverted how it handles this positioning after many years of doing it the other way. Now, when I invoke Manage Bookmarks, I find myself way down at the bottom of the list. All my recently added items are on top, so I have to scroll all the way up to get to them. Every. Single. Time. By the way, if user configuration of the Bookmarks system is implemented, it might be nice to have it be accessible through a menu at the top of the Library window rather than just something under Tools->Settings, or worse.
2. The Add Bookmark and Edit Bookmarks dialogues (Ctrl+D) have a fixed-size drop-down menu (the leftmost menu) showing folders sorted in order of most recent addition. Having the number of items in this menu be a fixed parameter is a serious and completely unnecessary impediment. Make the number of items user configurable, or make the menu dynamically resizable, or make it scrollable like the right-hand menu containing all items is. Making it scrollable -- a trivially easy UI change -- would all by itself result in an enormous increase in usability. Often items that ought to be in the left-hand menu get "aged out" unnecessarily because the list is too short.
3. For both the left and right menus in the Add Bookmark dialogue, small menu sizes are a usability impediment, and a big frustration in situations where they're an unnecessary constraint -- such as my laptop with a 17" 4K display with plenty of room to show more items at a single time. Scrolling through a very long list of items in a dialogue that's only willing to show you a few of them at a time is a special kind of hell and inefficiency. Make those menus resizable (by dragging the corner), or make their size user configurable, or adjust their size automatically based on the capabilities of the current environment. In other words, do something more reasonable than what's currently being done.
4. The availability of tags notwithstanding, bookmarks are still substantially organized in folders. Which, to be clear, is completely fine with me. But when I Search Bookmarks in the Library, for some perverse reason the search results don't tell me which folder each result lives in. How can that be? Often I would like to perform searches specifically so I can find a particular folder and examine other related items in that folder. The search mechanism and its results ought to be aware of and report on folders, not just bookmarks. A "Search For Folder" capability might be useful, but at a minimum all bookmarks in a result list should indicate the folder where they live.
5. This is a minor irritation compared to the others, but having the Add Bookmark (Ctrl-D) dialogue stash the bookmark somewhere arbitrary and close if you don't mouse over the dialogue really fast seems awfully presumptuous. Don't be presumptuous. More people will be irritated than will be appreciative, and that's a nice rule of thumb for all kinds of functionality that some designer thought was nifty and people trip over inadvertently all the time in their interactive environments. (Microsoft, are you listening?)
Feels like you could open a seperate idea for each of your points.
I rather like that the bookmarks are appened at the end ... but i guess an about:config option for people who prefer it otherwise wouldn't hurt.
You might also like this: https://addons.mozilla.org/firefox/addon/bookmark-tab-here/