S7comm node, Float presicion

Hello, I am reading approximately 100 variables of a PLC, using the "all variables" mode, the floating ones return values ​​such as "28.28429031372" and I only need to have a presicion of 5 digits.
When using the output of all the variables in a single message it is impossible for me to process a function like doPresicion to reduce the number of decimals ...
Any ideas?

It is good practice to keep them at full precision except when you want to display them. The dashboard nodes can be told what format to use, for example you can use
{{value | number:3}}
To show three decimal places.
If you really need to do it in javascript you can use toFixed() to do it.

Thanks for your answer, I'm actually taking the data in a string by MQTT, therefore I can not treat them individually ...

The string has a format like this: lcc, database = lcc-mqtt dn_RealTemp_inf = 44.12031936645508, dn_RealTemp_sup = 45.53071212768555, dn_SetTemp_inf = 45, dn_SetTemp_sup = 45, dn_RealAirTemp_inf = 49.5, dn_RealAirTemp_sup = 56.70000076293945, dn_PIDHeat_Inf = 76.23782348632812

but with about 100 values

So your problem is not reducing the precision, it is extracting the values from the string.
Do you have control over the data being published to MQTT? If so then it would be much better to change that so that either it writes the individual values to separate topics, or it is written as a JSON string.
If you cannot change that then the first thing is to split the string at the commas. You can either do that in a function node or using a Split node.