Appending linked record to existing list of linked records

First, here’s what I’m trying to do:

I’m working on an inventory for my video game collection. I have some games that are collections of other games. For example, ‘Metal Slug Anthology’ is a collection of 7 different Metal Slug Games. I have a record for the anthology, and 7 other records for the games that it collects. I have one field to show which games the anthology collects, and another field to show which collection the games are a part of. So the anthology shows the 7 games it collects in the ‘Collects’ field, and the 7 games each show that they are collected in ‘Metal Slug Anthology’ in the ‘Collected In’ field. Here is what it’s supposed to look like:

image

I’m trying to use an automation so that when a game is shown to be collected in another game, that game automatically shows that it collects the first game. That is, if I were to update the ‘Collected In’ field for Metal Slug 3, then Metal Slug 3 would automatically show in the ‘Collects’ field for Metal Slug Anthology. Here is the automation I’m using, triggered when the ‘Collected In’ field is not empty:

Screenshot 2021-09-25 223333

What I’m trying to automate is when I choose that a game is collected in another game, the collection is automatically updated with the collected game in the ‘Collects’ field, so that I don’t have to manually choose records every time. When the automation is triggered it only replaces the current record in the ‘Collects’ field, and I’m trying to append it. I’ve found 2 posts that talk about appending a linked record to another list of linked records by first inserting the original list of linked records, but they don’t specify exactly how to do that. Here they are:

and

Is this accomplished solely in the update record automation? Or do I need to use a formula as well?

Any help would be appreciated!

Edit: in trying to get this to work I’ve found I’ve used over 90% of this month’s automation runs. Figuring out how to get this to work with just a formula would be really nice.

It looks like you want same-table backlinks. It is not possible with just a formula.

If you’ve used over 90% of your monthly automation runs only doing tests, using automations may not be the right method for this.

An alternative is to use a script that creates same-table backlinks. (Scripting is free until March.) There are some scripts in this thread, although you may need to wade through the posts to find one you like.