From the 2.1.3 manual
https://wiki.librecad.org/images/2/20/LibreCAD_Users_Manual_2.1.3.pdf page 37:
Aligns entities or text with similar. The cursor changes to a hatched cross and the command line says:
Select objects; (select one or more [window] then press enter key).
Select base point (from previously selected objects).
First target point (snap to proposed grid point etc.)
Second base point (other 'end' of original location entity)
Second Target point (moved to selected position)
Do not forget to close the selection with enter.