Drop down menu through url session create

Through paypal it is possible to create buttons with a dropdown selection.

Example : https://www.paypal.com/ncp/payment/[token]

I am having hard time implementing the same through a session url, as I'd need to also include custom Ids for the whole process, and backend logic.

When creating a normal monthly sub I use:

const response = await fetch('https://api-m.paypal.com/v1/billing/subscriptions', {        method: 'POST',        headers: {            Authorization: `Bearer ${accessToken}`,'Content-Type': 'application/json',        },        body: JSON.stringify({            plan_id: 'P-08L0057...',             custom_id: `${customId}`,             application_context: {                brand_name: 'Sub',                locale: 'en-US',                shipping_preference: 'NO_SHIPPING',                user_action: 'SUBSCRIBE_NOW',            },        }),    });    const data = await response.json();    return data;

Is there a similar way, but to display a dropdown with selectable options instead?Or do I have to make the dropdown myself and then creating an order based on that?

  const response = await fetch('https://api-m.paypal.com/v2/checkout/orders', {        method: 'POST',        headers: {            Authorization: `Bearer ${accessToken}`,'Content-Type': 'application/json',        },        body: JSON.stringify({            intent: 'CAPTURE',            purchase_units: [                {                    amount: {                        currency_code: 'EUR',                        value: '6.75',                        breakdown: {                            item_total: {                                 currency_code: 'EUR',                                 value: '6.75'                            }                        }                    },...

The problem with this approach is that it stacks up all the options I'm trying to give.