Lock movement to vertical or horizontal

How can I move an object perfectly vertically or horizontally?

When I move it freely with the mouse, I often miss exact vertical
or horizontal alignment.

From Flywire's answer to that other thread:
Restrict Vertical/Horizontal: This option can be found in the snap toolbar. If you start a line or other entity with this restriction off, you can then activate it to constrain the end of the entity to a vertical or horizontal alignment relative to the starting point.

https://forum.librecad.org/Converting-to-Libre-CAd-from-Turbocad-td5728036.html#a5728037

The line already exists.  

Selecting the line with Restrict Vertical, the horizontal line does move up or down,
but the left endpoint shifts to the right rather than staying a the same x position.

Ah, after checking I have to see there really is a problem. The moved line seems to jump to the axis of the Relative Zero position, and the direction depends on whether you grip the line at the part nearer or farther to relative zero.

If you use Modify - Move/Copy this does not happen. But it takes more clicks that way.

You may also download one of latest 2.2.2 alpha versions (available there https://github.com/LibreCAD/LibreCAD/releases/tag/2.2.2_alpha-latest).

There I've added possibility to move selected entitites by keyboard (left/right/up/down).

With that mode - both of endpoins are moved correctly.

More info is there:

https://github.com/LibreCAD/LibreCAD/pull/2286

Demo Video: https://youtu.be/frAccXDuTIk

well, yes, but if the position of relative point will be moved to one of endpoints - the entire line will be moved properly.