I am not sure of your programming expertise but generally, as EPESI is open source software, you can do anything.
If you do not see the dot it means that developers have probably used the values of these field in the code and therefore disabled the modification and deactivation.
It is also possible that this is not the case but simply the field was overlooked and not declared as "extra" enabling you to modify it from the GUI
What you can do is:
- check the code if the any of the fields you want to deactivate are mentioned / used
- open the premium_salesopportunity_field table in a DB editor and change value of "extra" from 0 to 1 on fields that are not used and you like to deactivate
- extensively test the module
It is best if you do this on a development installation.