Alright, so the first thing you want to do in Xano is get to the API endpoint. This is where you can handle all sorts of actions for your data. Think of it as the control room for your records.

Next up, let's build a bulk update API. Head over to the APIs section on Xano and find the 'Tables' option. Pick the table with the records you want to update. If you can't find 'Tables,' look under 'Server' and you'll see it labeled as 'Database.'

Now, you'll need a custom function to handle the bulk update. Scroll down to the 'Functions' field and hit the 'ADD' button to create a new one. Give it a name and maybe a description so you remember what it's for later.

In this function, you can add custom logic blocks to decide when the bulk update should happen and what it should change. Click 'ADD ACTION' and choose 'Update record.' Then, select the table with the records you want to update.

A dialog box will pop up. Here, you fill in the conditions to match the records you want to update. Then, specify which fields should be updated and what the new values should be.

Click 'DONE' to save everything. Your custom function for updating multiple records will now be in the function list. Run it to make sure it works as expected. Fingers crossed!

To update multiple records from an external app, you'll need to expose your custom function as an API endpoint. Then, you can send a PUT request to this API from your app to run the bulk update.

Don't forget to secure this API endpoint, especially if you're dealing with sensitive data. Use Authentication and Authorization blocks in the function workflow if needed.