Use of sales_quote_address_collect_totals_before events Magento 2.

You can use sales_quote_address_collect_totals_before event for setting your custom totals related data before Magento collect final totals for a quoted address.

Use of address collects totals before event inside observer, You can fetch specific quote data, shipping_assignment, and total related data for a cart.

The event is defined under the Magento_Quote/Model/Quote/TotalsCollector.php file of the Quote module.

You can be interested to retrieve  A Complete List of all events in Magento 2.

Using Event, You can set your custom data before the quoted address set final data.  Define events in events.xml file,

Create an Observer file to handle your custom data,

The event is used for handling customer address data before the final address and total are set for a quote.

Using the event you can customization of your quote address related stuff in Magento 2.