Challenge: QGIS Plugin to insert points in 'Local Cartesian' coordinates

In the previous post I create class, that allows easily to calculate latitude and longitude of point that is given in local Cartesian coordinates. Now it's time to make life even more easier - custom QGIS plugin. The  result is as below:

Points with column that keeps 'definition of point in local Cartesian system' as labels:
reference (origin) point ID, X, Y coordinates and their unit of measure.

Plugin can be download from: https://github.com/strpaw/QGIS3-PointByLocalCartesian