A general concern I tend to have as a Creator is finding ways to easily distinguish between what modes items are from, how certain items behave differently (like the normal Impulse Grenade vs. the Ballistic Impulse Grenade), or that certain versions of items may never find their way in Creative at all due to having differences only in sounds, visual effects, or other gameplay differences that don't make the item "worthy" of inclusion.
My solution to this problem would be to add a Content Drawer (like the ones for collaborations) for every distinct gamemode Fortnite currently offers (OG, Ballistic, etc.), in which the only prefabs, items, weapons, vehicles, etc. that appear in the content drawer are the ones used solely in the respective gamemodes.
Having a separate content drawer for each mode is much more effective than a tag system, as it filters which items you're looking for by mode a lot more reliably, it allows items that share models / sounds / effects to exist with the modifications made for their original mode in the Creative inventory, and minimizes confusion.
I understand not every item or weapon is meant to be added to Creative, but I'm sure many creators could make use of a more organized Creative inventory that provides tools based on the experiences they want to make.