Hey @Liam & @GuillaumeFg !
Based on Shopify documentation, this should be possible here
I needed this for my app so I did some investigation on how I can detect if app embed is added by user or not.
Here is what I have found using Remix.
In your loader function, first find the active theme ID, then read the settings_data.json file. The app embed data will be saved in this file when user enable it.
`
const activeTheme = await admin.rest.resources.Theme.find({
session: session,
role: ‘main’,
})
const settings_data = await admin.rest.resources.Asset.all({
session: session,
theme_id: activeTheme.id,
asset: {“key”: “config/settings_data.json”},
});`
It will return a json format.
`
{
“current”: {
“sections”: {
…
},
“content_for_index”: [
],
“blocks”: {
“17878678986028907411”: {
“type”: “shopify://apps/faceforms-better-pop-ups/blocks/app-embed/f2173231-e611-461d-884b-bd8e6cc2ded4”,
“disabled”: false,
“settings”: {
…
}
}
}
}
}
`
You can look for your own app embed data if exist in this json file.
“<block_unique_ID>”: {
“type:”: “<partner_name>://apps/<app_name>/blocks/<block_name>/<unique_ID>”
It it exist and enabled you can find out.
I hope it helps other too 
Thank you!