Same need here.
According to the Paypal Payment REST API, this option is not availiable. But there is an option, application_context.shipping_preference, which can be set to NO_SHIPPING to disable the shipping address (find in the SUPPORTED_REST_FIELDS object of the Paypal button script).

I submit a PR.

I am having the same problem. How to apply this? @jlttt
Thanks.

@renielDev You can have a look at the file changes of the PR #184.

You can use PayPal Web experience profiles - link. Just create customized profile and add parameter 'experienceProfileId' to your gateway initialization.

The PR referenced can't currently be merged because of code conflicts. I'll resolve that when I can.

Because this is still open for anyone who wants to disable the shipping during the payment using paypal rest api:

$transaction = $gateway->purchase($operation);
$data = $transaction->getData();
$data['application_context']['shipping_preference'] = 'NO_SHIPPING';
$response = $transaction->sendData($data);