Is there a way to select and delete all messages from a particular sender in Thunderbird instead of deleting them one at a time?
filter your messages by sender and delete them
You could always sort the messages based on the From: field, click on the first entry from the sender in question, scroll to the last entry for this sender and Ctrl-click on it to select this and all intervening messages, then press the delete key.
perhaps like this
go to the tools menu and select the option for filters
Gather the senders