UPDATE 7/12/2022: In addition to the customizer in thingiverse, you can customize your wall plate using one of these approaches:

1. Download OpenSCAD from http://openscad.org/ then open the attached .scad file. Use the Window -> Customizer menu item to open the customizer. Enter your parameters. Use the Design -> Render command. Then File -> Export.
2. Use https://models.makewithtech.com/ to open this model and customize it there. You will need to create a free account.

UPDATE 4/10/2021: Added support for keystone jacks. This is currently untested, please let me know if this works for you.

This wall plate customizer offers some unique customizations that I haven't found elsewhere.

1. spacer - for electrical boxes which protrude from the wall, such as in an unfinished garage or basement, this creates a deeper wall plate
2. offset opening - when you have an obstruction on one side

Plus you have your choice of sizes, devices, and border designs. You can have up to 6 devices (6 gang) on a single wall plate.

Sizes

"ANSI/NEMA WD 6-2016 Wiring Devices - Dimensional Specifications" defines standard dimensions for wall plates in the US. However it only defines a minimum size for the outer dimensions of 4.49" H x 2.74" W for a single-gang wallplate. Some manufacturers use this as their "standard" wall plate size and others go a little larger. There is no standardized naming for wall plate sizes.

This program provides a range of sizes in increments of 3/16". This aligns closely with commonly available wall plates and takes the guess work out of selecting a plate size. The width of the plate will grow by an equal amount.

Devices:

• toggle switch
• duplex outlet
• single outlet
• rocker switch or decora device
• despard devices: single, double, triple
• two pushbutton switch
• blank wall cover

Border Designs

• rounded edge
• art deco
• frame
• building brick studs
• diamond plate

Before printing a plate with the building brick studs, do a test print of a small block from Customizable LEGO-Compatible Brick. The same stud scale factor can be used here in the Advanced section of settings.

Safety Warning

ALWAYS be particularly careful when working on electrical projects and with electrical equipment. Be sure to positively identify each circuit with an electrical test meter or instrument and Turn Off Electrical Circuits BEFORE proceeding with any electrical work.

Compliance with Laws

ALWAYS follow electrical code requirements specific to your area, and before undertaking any home electrical project, contact your local electrical authority and your insurance company to ensure that you comply with all policies, warranties, regulations and authorities concerning this work. If you are at all unsure about completing any aspect of you wiring projects, consult a qualified electrical contractor to perform the service(s) for you.

Legal Disclaimer

This software is provided as is without warranties of any kind, either express or implied. You acknowledge, by use of the software and documentation, that use of it is at your sole risk and that you assume full responsibility for any and all costs arising from use of the software..