How can I create an EXT4 partition with an extra large number of inodes?

Using mkfs -t ext4 -N iNumberOfINodes /dev/XdY where iNumberOfINodes is a 32-bit number so the maximum possible number of inodes on any ext2/3/4 file system is 2^32-1, or 4,294,967,295 (~4 billion).

See the man page for mkfs.ext4.

man mkfs.ext4

Option -N allows you to set the number of inodes created in the filesystem, and option -I allows you to increase their size (so they can handle more extended attributes of files). Adjust to fit your situation when you create the filesystem.