Hello igulec,

at first welcome to the forum.

How do you change the Mq value with the panel? Through an I/O field?
If so, then you can not take the output value of the PI controller into the Mq parameter.

Then you would have to do 2 fields.
An I/O field indicating the last (stored) output value of the PI controller.
A second I/O field, with the Mq value.
In this second I/O field, you would then have to enter the value from the first I/O field.
Then use a button in the LOGO! Program to switch from the last saved output value of the PI controller to the value of the Mq value from the panel byusing an analog MUX.
Background is the following:
If you assign an HMI variable in the form of a block parameter to an I/O field in the panel, you can not write to this I/O field from another location

In attachment a possible solution to save the output value of the PI controller in the Mq parameter when switching off the automatic.
In order to avoid a recursion of the analog value, the Mq value is transferred to the VM memory and then read in again as an analog network input. The parameter VM mapping is used for this.

Then I did not understand your description correctly.
And the user Scorp, who also made a suggestion for you, understood it exactly as I understood it.

Then you have to describe more exactly what you want to do.
Do you want to use the buttons to set a setpoint that will be saved until it is changed again with the buttons?
No matter what value the controller outputs when switching off the automatic?

Or want you to make the output value as the Mq value, when you switch to automatic?

If yes, that is not possible.