The Filter Menu automatically synchronises tags with each filter collection. The process of syncing tags involves adding a tag that matches the collection handle to each item in that collection.
For example, the following collection contains items with a Product Type of "Jackets"
And the handle for this collection is "jackets"
To view the handle for any collection, open it in your Shopify admin and scroll to the bottom, then click on the "Edit Website SEO" link. This will open a new section showing the handle and some other SEO details. The handle is the text after "collections/" in the URL.
Back to the example, the Filter Menu will automatically tag each item in the "Jackets" collection with the "jackets" tag to match the collection handle.
If any products in your store have that same tag but are not in the collection, the tag will be removed. Keep in mind that the products must match the collection conditions to be included in the collection.
If this collection had an inventory condition as well, like "Inventory stock is greater than 0"
Then any items with the Product Type of "Jackets" that are also sold out will have the "jackets" tag removed, as they would not be present in this collection due to not meeting the collection conditions anymore.
This method works well with Product type collections, as the collection conditions do not rely on the tags to gather products.
Tag based collections with Inventory conditions
When the collection conditions use inventory and tags to gather products, an issue can arise where the Filter Menu removes the tag used to pull products into that collection. This will only occur when the tag used is the same as the collection handle.
Using the same collection as before, but this time with "Product tag is equal to jackets" instead of the Product Type:
This collection handle is still "jackets" which matches the tag "jackets"
Now when any item tagged with "jackets" is sold out, the item will be removed from the collection, on the next store update the Filter Menu will remove the matching tag, as that item is no longer in the Jackets collection. This is the normal behaviour for the app. However, it won't add the tag back when the item rises in inventory, because the item will not be present in the Jackets collection anymore.
If removing the Inventory condition is not an option, there are two possible solutions to this issue:
Change the collection handle.
Change the tag used to pull products into the collection.
Changing either one of these variables will allow the app to continue syncing tags to keep your filters up to date, and also allow the inventory rules to work correctly by removing out of stock items from your collections.
If you decide to change the collection handle, you will need to delete the filter for the collection and set up a new one, as the app cannot detect changes made to the handle. Any navigation links that used this collection handle may also need to be updated.
If you decide to change the tag used to pull products, you can use our Bulk Edit Tags app to quickly add the new tag to all of the items in the collection. The only requirement for the new tag is that it does not match the collection handle. You will also need to update the collection conditions to include items with the new tag.
If you have any additional questions, please contact support through the live chat in the app, or at firstname.lastname@example.org