Device Tested: Codesys Control Win V3 x64 (3.5.18.0)
Codesys Version: 3.5 SP18 64bit
Configuration:
Codesys is acting as a Modbus Slave (ModbusTCP Slave Device).
General Configured Parameters:
Holding Registers: 10 (%QW) Writeable
Input Registers: 10 (%QW)
Coils: 0
Discrete Inputs: 0
Data Model: 0/0/0/0
In a global variables list I declared the following:

UI_Word_1   AT %QW0 : WORD;
UI_Word_2   AT %QW1 : WORD;
UI_Word_3   AT %QW2 : WORD;

Behavior:
Unable to use the "Write Values" function in the Debug menu to set the value of variable mapped to the Modbus TCP Slave from Codesys. I am able to successfully write to the variable from within the logic. I am able to successfully force the value. After releasing the force, the forced value is retained.

Unable to use the "Write Recipe" function to update mapped variables.