#1. First, use Squarespace ID Finder to find the ID of the Text block
In my example, it is:
- #block-yui_3_17_2_1_1722297840428_27530
#2. Use this code to Custom CSS box
#block-yui_3_17_2_1_1722297840428_27530 ul {
padding-left: 0px !important;
}
#3. Result