Your best bet is ask questions here, there is relatively little documentation. The fzp specifies pretty much everything, that is what the parts editor is modifying. For renumbering, I generally use this script to create the number of pins I need and then use a text editor to replace the current connector definitions. Then I just need to set the name and description fields.
The connector definition sets all the values in the svg. As an example here is the first connector from your fzp file:
<connector type="male" id="connector0" name="pin 1">
<description>Pin 21, SDA, GPIO21, V_SPI_HD</description>
<views>
<breadboardView>
<p svgId="connector0pin" layer="breadboard"/>
</breadboardView>
<schematicView>
<p terminalId="connector0terminal" svgId="connector0pin" layer="schematic"/>
</schematicView>
<pcbView>
<p svgId="connector0pin" layer="copper0"/>
<p svgId="connector0pin" layer="copper1"/>
</pcbView>
</views>
</connector>
for each view svgId=“connector0pin” defines the pin name in the svg. If no terminalId=“connector0terminal” is present, the connection will be made in the center of the svgId element. In the breadboard case, since they are circles and that is where we want the connection we skip the terminalId. In schematic the pin is usually a line or rectangle, and we want the connection to be at one end or the other of the pin, so the terminalId is usually a rectangle that is centered on the end of the pin (that is what the Select graphic for pin does. As far as I know it needs the pins defined in the svg. It will then put the terminalId on the selected end of the pin, but I think only if there is already a terminalId defined. If you haven’t seen them this set of tutorials covers the current Fritzing versions (many of the others on the net are for older versions):
Part creation howto part 1 breadboard and pcb
there are currently 9 of them as I try and document all the stuff I have learned from folks in here (most of who are no longer posting.)
Peter