You can sell supplies to get money.

This is rarely needed in PCC because PCC automatically sells supplies when needed. When supplies are sold, they are gone (aside from undo later this turn); you cannot buy supplies from money.

The "Sell Supplies" dialog will ask you how many supplies you want to sell. It will sell the supplies when you confirm with Enter. You can also enter the number of supplies you want to keep and confirm with A.

Reference

Keys:
S from planet screen
This is a testing version.
It may be incomplete, and have more bugs (or features) than the public live version at planetscentral.com.