Shard Trimmer

Soul Shards pile up fast and eat your bag space. ShardTrimmer counts the shards in your bags, tells you when you're over your limit, and removes the extras for you, safely and only when you click.
Available for WoW Forever and WoW Classic Era. Download the file that matches your game: the file names and game versions on the Files tab tell them apart.
Features
Pick your limit. Choose how many shards to keep (0 to 60), and each click deletes the extras above it.
An action bar counter. One click creates a macro whose name shows your count and limit, like 02/03. Drop it on your bar and the button glows softly when you're over your limit. Press it to trim. Sliders set how big the counter text is and nudge where it sits on the button. Works on the default action bars and Bartender4.
Fewer clicks. The game only lets an addon delete one stack per click, so in WoW Forever ShardTrimmer merges your shard stacks automatically while you're out of combat. Each click then removes as much as possible, and the button shows how many clicks are left.
Delete a set number of shards instead, if you prefer.
Safe by design. Nothing is ever deleted until you tick a confirmation box, and then only when you click or press the hotkey. Only Soul Shards in your bags are touched, never your bank.
Key binding for "Delete extra soul shards" under Key Bindings → AddOns.
How to use
Type /shards to open the settings window, or use the minimap button or Options → AddOns → ShardTrimmer. /shards count shows your total, and /shards trim deletes the next batch of extras.
Classic Era: one shard per click, soul bag kept for last
In Classic Era soul shards don't stack, so each click (or key press) deletes one shard, and the button shows how many clicks are left. Shards in your regular bags are deleted before the ones in a soul bag (Soul Pouch, Felcloth Bag and so on), so your regular bag space frees up first.
Disclaimer
ShardTrimmer is one of a few addons I came up with to make quality of life easier for myself during the WoW Forever beta test. The ideas are my own, and I did not search for, look at, or use any other author's addons, code or artwork before making them. Any resemblance to existing addons is coincidental. Made for WoW Forever and WoW Classic Era. Released under the MIT license.