Because you are actively editing the design in memory, changes are automatically passed to downstream tools for the remainder of the Vivado IDE Tcl session. This enables you to reflect the changes in the active design and to save the changes for future attempts. Select to save constraints changes for future use. You can use this command to write a new constraints file or override your original file.
write_xdcTcl command is run. For more information, see the Vivado Design Suite Tcl Command Reference Guide (UG835).