I'm loving the tool. I been using an SQL database to build my records but I find this interface to be much easier to work with.

But I'm having some difficulty getting collections of references to work, which is unfortunate because I'm using references heavily to make abilities and bonuses modular.

I'm not confident of the Repro steps, because it seems to fail intermittently but it fails quite a bit. Essentially new references added to the collection will often fail to point to the assigned reference. The Drop down just comes up empty.  I've had to add reference collections multiple times in order to get them to take, and it seems like if you try to edit them it just farts. I've also had cases where I assign to a refrence collection a particular category, but the collection refuses to point to it, instead selecting another category despite repeated attempts to get it point to the right category
I am using nested references, but not circular refrences.

IE AbilityResource  contains many  AbilityEffectGroups each of which contains one or more EffectResources.

This is important because it's a tactical RPG I'm making where I need to have the ability to set up various targeting groups for spells that have multiple targets, but have fine control of the status effects / damage inflicted on each target.

anyone else run into this and any insight into how to troubleshoot or work around it?

Addendum -

There are 2 separate issues here after further exploring it.

1 ) When adding a new reference collection at the root level of a category, it will add a default entry. If you remove that default entry, you can no longer edit the reference category in the collection edit interface, and your only able to add blank references on items inside a category. IF you add the default reference back you can then edit the reference category.

This is a minor issue, though as a quality of life improvement I'd like to be able to have a default reference type set for a collection without requiring it to actually have an entry, since an empty collection is still valid.  I'm able to work around this by removing the default reference inside each individual item.

2 ) I do think this falls down when references are nested. So if I have a reference category pointing to a thing that also has a reference collection inside of it, it will never correctly assign itself to the proper category. So I definitely would like the developer to look into this if he can. 

It's also possible it's failing silently somewhere ( Like a broken record somewhere ), but in either case I'm not getting expected behavior. 

 For the moment I won't be using nested references and I'll just build the intervening layer in code on game boot up and store the raw data flat, but it's a bit of a hacky approach I'd like to avoid.

So far my collections of references have been working without issue, however, I have not had complex uses as you have mentioned yet. Ill keep you posted if I run into similar things

Understood. 

I've actually opted to not use Gridless for this project sadly. I did have a DB oriented solution already that was I was going to replace, but the issues with collection reference made it more difficult than it was worth at the moment. 

I REALLY like the tool. The interface is clean and simple, and it's easy to mock out really complicated data in an intuitive way.  I think it needs a little more polish for what I need though, so I'll revisit it in the future. Especially if I can keep Gridless in mind as I'm building the schema for my next project. It's not hard to match a new project up to it, but an old project that isn't going to cache everything from a single Json file would require some changes that don't add enough value for the time I'd need to spend.

There is a new version up - 1.22, which improves references and collections: https://radmatt.itch.io/gridless/devlog/268880/update-122-improvements-and-fixes

I'm glad you liked the tool and hopefully this update will improve Your experience with it, if You decide to give it another try.