I could go for each components and click on the value and change it from f.fab to silklayer but I wonder if there is a faster way of doing so?
Depending on how many components we’re talking about, the easiest way would be to open the PCB file in a text editor and do a search-and-replace.
A Python script would be another way, if you have lots components.
Method 1: Go to Edit > Text and Graphic Properties and change the layer for all values
Method 2: Set selection filter to text only, set object visibility so that you see only the values, make a box selection to select all values, change the layer in the property editor