NodeMCU Power supply
Yes, you may connect all 3V pins together (red) and all GND pins together (black), like so:



In some cases, more wires will improve the circuit. E.g. when you build the Ben Eater 8-Bit CPU, you'll find that connecting power in a ring instead of a line will reduce voltage drop by about 50%.



When first reading your question, I got the impression that you wanted to solder the 3.3 V wires directly to the voltage regulator. Here's my original answer for that:

That's not a good idea: if you connect the same wire to all pins, your're creating a short, typically causing a malfunction if not worse. You may destroy your equipment (external board as well as the NodeMCU v3). Do NOT connect 3.3V to all pins of the voltage regulator. 

A voltage regulator has 3 pins:


voltage in (for an unregulated voltage you can't exactly control; typically higher than the output voltage)
voltage out (for the stabilized resulting voltage you want to have)
ground


The only pin to connect the voltage to is the "voltage in" pin (VIN). And typically, a development board has a pin for that:



However, you'll find that the input voltage must be between 4.75V and 10V, so supplying 3.3V from an external board is not sufficient.

If you have regulated (stable) 3.3V already, you can connect that to a pin labelled 3V:



Also, you need to connect the grounds (GND) of both circuits together (GND of external board to GND of NodeMCU), otherwise the current will not find its way back.