I came up with two options:

• Making a canvas [cnv] object and sending a label message to it. This works, but I need to use [makefilename %d] because [cnv] complains if the label message contains only a float.
• Using a number or number2 object would be my ideal choice but I don't want the user to be able to change it. Is there a way to «disable» or make the number GUI element static?

Thanks

You can check this module that i made. It contains a feedback monitor screen for reading parameters. See the small "wave_sweep<-0.61" canvas in the imagine. It shows the values of the sweep hslider.

WaveMaker patch download :
WaveMaker.zip

Here is a more simplified version to show how to do it :
ParameterFeedbackScreen.zip

OBS ! the "$0-clear-send" names come from right-click on each objects and set under "Messeges" the "send symbol" and "receive symbol" so that you don't need to use wiring between GUI objects. The "send symbol" is the output of that object and the "receive symbol" is the input. the "$0" symbol is used so that you can have the same GUI multiple times in the same patch without problems. You can also change in "label p1-$1" like "label Value:->$1" so in canvas will look like "Value:-> [your parameter value]" for aesthetics purpose.

snapshot :

If this is for your own machine that will be left somewhere for the public to use then you could set kiosk mode with a plugin......... https://puredata.info/downloads/kiosk-plugin
You can disable key bindings and the window menu...... so you could stop the user entering editmode and use a message box for your fixed value.
David.

I ended up using this solution:

The user won't be able to change value if the range is fixed.