It would be great to add an extra validation on a Single / Multiple links field, where you could specify a filter. So for example on an model Cars Page which includes Articles:
Cars Page -> Multiple Links field -> Article model with category cars
In this way, we can limit the client’s input only to that with category Cars, and only these will be visible and accepted. This would be super helpful with big datasets on dato.
Thanks 
I would like to 2nd this.
YES! @wonderlandams this would be sick! I think this is such a valuable add. More features like this continue to eliminate the need for people to reach for something like Sanity to customize validations.
I have this need presently where we have an and Article Section model that has a Multiple Links “Featured Articles” field. It would be great if limit editors to only selecting Articles from the respective category.
I also love the idea of it being Filter based. In the same way we build menu items in Dato that can reference a filter I could see “Apply saved shared filter” working in conjunction with “Accept only specified model” so that when and editor hits “From Library” the modal that comes up will be prest to that applied filter.
Only thing that makes me think twice there is what about a model like “Author” with a similar Multiple Links “Featured Articles” field. It is possible to imagine creating filters for every Category (not a ton of those), but a filter for every Author seems impractical to manage. This leads me to believe a powerful rule based condition is gonna be needed to really ensure this is reliable for multiple use cases.
Dug into this a bit. It looks like there may be a pathway here with the plugin SDK.
ctx.selectItem would open the modal, and there appears to be an undocumented ‘initialLocationQuery’ that can be passed as an option. In theory we could pass in some filter values based on data on the current record such as ‘authorId’ or ‘categoryId’ in my case.
If I have time to play with it I’ll report back.
Okay, so I made SOME progress, but feel like I’m missing something here. Let’s assume we are on an author record on “multiple links” field that will accept articles.
I made a field extension with plugin sdk with a button that calls the following:
ctx.selectItem('article-content-model-id', {multiple: true, initialLocationQuery: {
filter: {
query: '',
fields: {
'author': {
eq: ctx.item?.id
}
}
}
}})
This actually “works” as expected in that it launches the library modal dynamically filtered down to the author of the record I’m viewing.
The downside is that it seems as a side effect I’m forced to lose all the UI from the default field extension and it doesn’t appear in the plugin design system that there is an obvious way to recreate it.
I though maybe if I made this as an add on extension I could pass the initial initialLocationQuery filters to the field without having to render any UI, but haven’t been able to figure it out.
@roger forgive that @ mention, it’s just that you’ve been super helpful on my other posts.
Hey @brian1,
You can totally do this with a plugin! If you make a “field addon” instead of “field editor”, it will keep the original editor too: Field extensions — Plugin SDK — DatoCMS
It ends up working like this:
The component file, in this case components/FilteredLinkField.tsx, looks like this:
import {Canvas, Button} from 'datocms-react-ui';
import {RenderFieldExtensionCtx} from "datocms-plugin-sdk";
type PropTypes = {
ctx: RenderFieldExtensionCtx;
};
export const FilteredLinkField = ({ctx}: PropTypes) => {
const chooseFilteredItem = async () => {
const selectedRecords = await ctx.selectItem('CAm14tHtS1yvtZ_tkzSEww', {
multiple: true, initialLocationQuery: {
filter: {
fields: {
'author': {
eq: ctx.item?.id
}
}
}
}
})
if (selectedRecords?.length) {
await ctx.setFieldValue(ctx.fieldPath, selectedRecords.map(record => record.id))
}
}
return (
<Canvas ctx={ctx}>
<Button type="button" onClick={chooseFilteredItem} buttonSize="s">
Filter
</Button>
</Canvas>
);
};
And the index.tsx for the plugin:
import {connect, Field, FieldIntentCtx, RenderFieldExtensionCtx} from 'datocms-plugin-sdk';
import 'datocms-react-ui/styles.css';
import { render } from './utils/render';
import {FilteredLinkField} from "./components/FilteredLinkField";
connect({
overrideFieldExtensions(field: Field, ctx: FieldIntentCtx) {
if (field.attributes.field_type === 'links') {
return {
addons: [
{ id: 'filteredLinkField' },
],
};
}
},
renderFieldExtension(fieldExtensionId: string, ctx: RenderFieldExtensionCtx) {
switch (fieldExtensionId) {
case 'filteredLinkField':
return render(<FilteredLinkField ctx={ctx} />);
}
},
});
Here’s an example plugin if you’d like to see it: filtered-link-field-example/src/components/FilteredLinkField.tsx at main · arcataroger/filtered-link-field-example · GitHub
(But please note that this will currently affect ALL multi-link fields. You can configure that in index.tsx; see documentation for automatic or manual overrides.)
Hope that helps!
PS Please always feel free to @mention me, but if you ever want to make sure someone sees your post, emailing support@datocms.com is a better guarantee 
I check the forum almost every day, but the email will get to the whole team in case I’m out of the office.