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.

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

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

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,

Event is used for handling customer address data before final address and total is set for a quote.