Add a warning icon with the FA icon (<i class="fa-solid fa-triangle-exclamation"></i>) to the following places could work for cases where a missing backend is reported. The button/icon can be hidden if everything is okay.

For jobs, services, files, UDPs a button with icon should work, for collections, processes, file formats it might just be a clickable icon without button style as it might look more pleasing.

The JS client v2.7.0 supports the functionality to retrieve the properties since some months, see also Open-EO/openeo-js-client@fd78bb8 and Open-EO/openeo-js-client@2a14de7

The list of missing backends with a short explanation could be shown in a modal, toast or tooltip.

High prio tasks should be implemented first.
This can be implemented directly to the openeo-web-editor as PRs to the main branch, we can merge this later into the gdc-web-editor repo.

Regarding the issue that we don't really like a tooltip on a button, but a modal would also be overkill:

How would you like a "compact" version of the FederationMissingNotice for the panels? Which styling is desired could be set via a boolean compact prop.

Consumes one line of space (two if the availability situation is really bad or the screen particularly small), but would be consistent with the rest and IMO fairly pleasing visually.

I like that. I'd also expect that usually it's only a single backend, so the text should usually be a bit shorter.

Nice, then I'll finish implementing that.

For now I made it as a separate component in the templates of the panels (requiring to wrap everything in a new <div> to ensure only 1 root element), e.g. like this in JobPanel:

<template>
	<div id="JobPanel">
		<FederationMissingNotice ... />
		<DataTable ... >
			<template slot="toolbar">
				...
			</template>
			...
		</DataTable>
	</div>
</template>

Or would you prefer adding a new slot to DataTable? Would then look like this:

<template>
	<DataTable ... >
		<template slot="notice">
			<FederationMissingNotice ... />
		</template>
		<template slot="toolbar">
			...
		</template>
		...
	</DataTable>
</template>

The latter would give the option to switch the places of toolbar and notice, but I prefer the current layout anyway (tools to manipulate the table are directly above it, not split from it by an annoying notice). Semantically I think one could find arguments for either version.

I think I'd go with the first option, that seems a little more clean.
You'd need to make sure that the scrolling etc still works as before.

First real-world displaying of fed:missing information :)) [when connecting to openeo.cloud, i.e. no stump]